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Rabu, 18 Maret 2009

Animal Minds

This article surveys philosophical issues related to the nature and scope of animal mentality, as well as to our commonsense understanding and scientific knowledge of animal minds. Two general sets of problems have played a prominent role in defining the field and will take center stage in the discussion below: the problems of animal thought and reason, and the problems of animal consciousness.

The article begins by examining three historically influential views on animal thought and reason. The first is David Hume’s analogical argument for the existence of thought and reason in animals. The second is René Descartes’ two arguments against animal thought and reason. And the third is Donald Davidson’s three arguments against ascribing thought and reason to animals.

Next, the article examines contemporary philosophical views on the nature and limits of animal reason by Jonathan Bennett, José Bermúdez, and John Searle, as well as four prominent arguments for the existence of animal thought and reason – the argument from the intentional systems theory by Daniel Dennett, the argument from common-sense functionalism by Jerry Fodor, Peter Carruthers, and Stephen Sitch, the argument from biological naturalism by John Searle, and the argument from science by Colin Allen and Marc Bekoff, and José Bermúdez.

The article then turns to the important debate over animal consciousness. Three theories of consciousness – the inner-sense theory, the higher-order thought theory, and the first-order theory – are examined in relation to what they have to say about the possibility and existence of animal consciousness.
The article ends with a brief description of other important issues within the field, such as the nature and existence of animal emotions and propositional knowledge, the status of Lloyd Morgan’s canon and other methodological principles of simplicity used in the science of animal minds, the nature and status of anthropomorphism employed by scientists and lay folk, and the history of the philosophy of animal minds. The field has had a long and distinguished history and has of late seen a revival.

1. The Problems of Animal Thought and Reason

Given what we know or can safely assume to be true of their behaviors and brains, can animals have thought and reason? The answer depend in large measure on what one takes thought and reason to be, as well as what animals one is considering. Philosophers have held various views about the nature and possession conditions of thought and reason and, as a result, have offered various arguments for and against thought and reason in animals. Below are the most influential of such arguments.

a. Hume’s Argument for Animal Thought and Reason

David Hume (1711-1776) famously proclaimed that “no truth appears to be more evident, than that beast are endow’d with thought and reason as well as men” (1739/1978, p. 176). The type of thought that Hume had in mind here was belief, which he defined as a “lively idea” or “image” caused by (or associated with) a prior sensory experience (1739/1978, p. 94). Reason Hume defined as a mere disposition or instinct to form associations among such ideas on the basis of past experience. In the section of the Treatise entitled, “Of the Reason of Animals,” Hume argued by analogy that since animals behave in ways that closely resemble the behaviors of human beings that we know to be caused by associations among ideas, animals also behave as a result of forming similar associations among ideas in their minds. Given Hume’s definitions of ‘thought’ and ‘reason,’ he took this analogical argument to give “incontestable” proof that animals have thought and reason.

A well-known problem with Hume’s argument is the fact that ‘belief’ does not appear to be definable in terms of vivid ideas presented to consciousness. Beliefs have propositional content, whereas ideas, as Hume understood them, do not (or need not). To have a belief or thought about some object (e.g., the color red) always involves representing some fact or proposition about it (e.g., that red is the color of blood), but one can entertain an image of something (e.g., the color red) without representing any fact or proposition about it. Also, beliefs aim at the truth, they represent states of affairs as being the case, whereas ideas, even vivid ideas, do not. Upon looking down a railway track, for instance, one could close one’s eyes and entertain a vivid idea of the tracks as they appeared a moment ago (i.e., as converging in the distance) without thereby believing that the tracks actually converge. And it is further argued, insofar as ‘belief’ fails to be definable in terms of vivid ideas presented to consciousness, ‘reason’ fails to be definable in terms of a disposition to form associations among such ideas; for whatever else reason might be, so the argument goes, it is a surely a relation among beliefs. Finally, and independently of Hume’s definitions of ‘belief’ and ‘reason,’ there is a serious question about how incontestable his analogical proof is, since similar types of behaviors can often be caused by very different types of processes. Toy robotic dogs, computers, and even radios behave in ways that are similar to the ways that human beings behave when we have vivid ideas presented to our consciousness, but few would take this fact alone as incontestable proof that these objects act as a result of vivid ideas presented to their consciousness (Searle 1994).

b. Descartes’ Two Arguments Against Animal Thought and Reason

Equally as famous as Hume’s declaration that animals have thought and reason is René Descartes’ (1596-1650) declaration that they do not. “[A]fter the error of those who deny God, “ Descartes wrote, “there is none that leads weak minds further from the straight path of virtue than that of imagining that the souls of beasts are of the same nature as our own” (1637/1988, p. 46). Descartes gave two independent arguments for his denial of animal thought and reason, which have come to be called his language-test argument and his action-test argument, respectively (Radner & Radner 1989).

i. The Language-Test Argument

Not surprising, Descartes meant something different from Hume by ‘thought.’ In the context of denying it of animals, Descartes appears to take the term to stand for occurrent thought – that is, thoughts that one entertains, brings to mind, or is suddenly struck by (Malcolm 1973). Normal adult human beings, of course, express their occurrent thoughts through their declarative speech; and declarative speech and occurrent thoughts share some important features. Both, for example, have propositional content, both are stimulus independent (i.e., thoughts can occur to one, and declarative speech can be produced, quite independently of what is going on in one’s immediate perceptual environment), and both are action independent (i.e., thoughts can occur to one, and declarative speech can be produced, that are quite irrelevant to one’s current actions or needs). In light of these commonalities, it is understandable why Descartes took declarative speech to be “the only certain sign of thought hidden in a body” (1649/1970, p. 244-245).

In addition to taking speech to be thought’s only certain sign, Descartes argued that the absence of speech in animals could only be explained in terms of animals lacking thought. Descartes was well aware that animals produce calls, cries, songs, and various gestures that function to express their “passions,” but, he argued, they never produce anything like declarative speech in which they “use words, or put together other signs, as we do in order to declare our thoughts to others” (1637/1988, p. 45). This fact, Descartes reasoned, could not be explained in terms of animals lacking the necessary speech organs, since, he argued, speech organs are not required, as evidenced by the fact that humans born “deaf” or “dumb” typically invent signs to engage in declarative speech, and some animals (e.g., magpies and parrots) who have the requisite speech organs never produce declarative speech; nor could it be explained as a result of speech requiring a great deal of intelligence, since even the most “stupid” and “insane” humans beings are capable of it; and neither could it be explained, as it is in the case of human infants who are incapable of speech but nevertheless possess thought, in terms of animals failing to develop far enough ontogenetically, since “animals never grow up enough for any certain sign of thought to be detected in them” (1649/1970, p. 251). Rather, Descartes concluded, the best explanation for the absence of speech in animals is the absence of what speech expresses – thought. There are various places in his writings where Descartes appears to go on from this conclusion to maintain that since all modes of thinking and consciousness depend upon the existence of thought, animals are devoid of all forms of thinking and consciousness and are nothing but mindless machines or automata. It should be noted, however, that not every commentator has accepted this interpretation (see Cottingham 1978).

Various responses have been given to Descartes’ language-test argument. Malcolm (1973), for example, argued that dispositional thinking is not dependent upon occurrent thought, as Descartes seemed to suppose, and is clearly possessed by many animals. The fact that Fido cannot entertain the thought, the cat is in the tree, Malcolm argued, is not a reason to doubt that he thinks that the cat is in the tree. Others (Hauser et al. 2002), following Noam Chomsky, have argued that the best explanation for the absence of speech in animals is the not the absence of occurrent thought but the absence of the capacity for recursion (i.e., the ability to produce and understand a potentially infinite number of expressions from a finite array of expressions). And others (Pepperberg 1999; Savage-Rumbaugh et al. 1998; Tetzlaff & Rey 2009) have argued that, contrary to Descartes and Chomsky, some animals, such as grey parrots, chimpanzee, and honeybees, possess the capacity to put together various signs in order to express their thoughts. Finally, it has been argued that there are behaviors other than declarative speech, such as insight learning, that can reasonably be taken as evidence of occurrent thought in animals (see Köhler 1925; Heinrich 2000).

ii. The Action-Test Argument

Whereas Descartes’ principal aim in his language-test argument was to prove that animals lack thought, his principal aim in his action-test argument is prove that animals lack reason. By ‘reason,’ Descartes meant “a universal instrument which can be used in all kinds of situations” (1637/1988, p. 44). For Descartes, to act through reason is to act on general principles that can be applied to an open-ended number of different circumstances. Descartes acknowledged that animals sometime act in accordance with such general rules of reason (e.g., as when the kingfisher is said to act in accordance with Snell’s Law when it dives into a pond to catch a fish (see Boden 1984)), but he argued that this does not show that they act for these reasons, since animals show no evidence of transferring this knowledge of the general principles under which their behaviors fall to an open-ended number of novel circumstances.

Some researchers and philosophers have accepted Descartes’ definition of ‘reason’ but have argued that some animals do show the capacity to transfer their general knowledge to a wide (or wide enough) range of novel situations. For example, honey bees that were trained to fly down a corridor that had the same (or different) color as the entry room into which they had initially flown automatically transferred this knowledge to the novel stimulus dimension of smell: those that were trained to choose the corridor with the same color, flew down the corridor with the same smell as in the entry room; and those that were trained to choose the corridor with a different color, flew down the corridor with a different smell as in the entry room. It is difficult to resist interpreting the bees’ performance here, as the researchers do, in terms of their grasping and then transferring the general rule, “pick the same/different feature” (Giurfa et al. 2001). Other researchers and philosophers, however, have objected to Descartes’ definition of ‘reason.’ They argue that reason is not, as Descartes conceived it, a universal instrument but is more like a Swiss army knife in which there is a collection of various specialized capacities dedicated to solving problems in particular domains (Hauser 2000; Carruthers 2006). On this view of intelligence, sometimes called the massive modularity thesis, subjects have various distinct mechanisms, or modules, in their brains for solving problems in different domains (e.g., a module for solving navigation problems, a module for solving problems in the physical environment, a module for solving social problems within a group, and so on). It is not to be expected on this theory of intelligence that an animal capable of solving problems in one domain, such as exclusion problems for food, should be capable of solving similar problems in a variety of other domains, such as exclusion problems for predators, mates, and offspring. Therefore, on the massive modularity thesis, the fact that “many animals show more skill than we do in some of their actions, yet the same animals show none at all in many others” is not evidence, as Descartes saw it (1637/1988, p. 45), that animals lack intelligence and reason but that their intelligence and reason are domain specific.

c. Davidson’s Arguments Against Animal Thought and Reason

No 20th century philosopher is better known for his denial of animal thought and reason than Donald Davidson (1917-2003). In a series of articles (1984, 1985, 1997), Davidson put forward three distinct but related arguments against animal thought and reason: the intensionality test, the argument from holism, and his main argument. Although Davidson’s arguments are not much discussed these days (for exceptions, see Beisecker 2001; Glock 2000; Fellows 2000), they were quite influential in shaping the direction of the contemporary debate in philosophy on animal thought and reason and continue to pose a challenging skeptical position on this topic, which makes them deserved of close examination.

i. The Intensionality Test

The intensionality test rest on the assumption that the contents of beliefs (and thought in general) are finer grained than the states of affairs they are about. The belief that Benjamin Franklyn was the inventor of bifocals, for example, is not the same as the belief that the first postmaster general of the US was the inventor of bifocals, even though both beliefs are about the state of affairs. This fine-grained nature of belief content is reflected in the sentences we use to ascribe them. Thus, the sentence, “Sam believes that Benjamin Franklyn was the inventor of bifocals,” may be true while the sentence, “Sam believes that the first postmaster general of the US was the inventor of bifocals,” may be false. Belief ascriptions that have this semantic feature – that is, their truth value may be affected by the substitution of co-referring expressions within their ‘that’-clauses -- are called intensional (or semantically opaque). The reason that is typically given for why belief ascriptions are intensional is that their purpose is to describe the way the subject thinks or conceives of some object or state of affairs. Belief ascriptions with this purpose are called de dicto ascriptions, as opposed to de re ascriptions (see below).

Our de dicto belief ascriptions to animals are unjustified, Davidson argued, since for any plausible de dicto belief ascription that we make there are countless other and no principled way of deciding which is the correct way of describing how the animal thinks. Take, for instance, the claim that Fido believes that the cat is in the tree. It seems that one could just as well have said that Fido believes that the small furry object is in the tree, or that the small furry object is in the tallest object in the yard, and so on. And yet there does not appear to be any objective fact of the matter that would determine the correct translation into our language of the way Fido thinks about the cat and the tree. Davidson concludes that “unless there is behaviour that can be interpreted as speech, the evidence will not be adequate to justify the fine distinctions we are used to making in attribution of thought” (1984, p. 164).

Some philosophers (Searle 1994; McGinn 1982) have interpreted Davidson’s argument here as aiming to prove that animals cannot have thought on the basis of a verificationist principle which holds that if we cannot determinately verify what a creature thinks, then it cannot think. Such philosophers reject this principle on the grounds that absence of proof of what is thought is not thereby proof of the absence of thought. But Davidson himself states that he is not appealing to such a principle in his argument (1985, p. 476), and neither does he say that he takes the intensionality test to prove that animals cannot have thought. Rather, he takes the argument to undermine our intuitive confidence in our ascriptions of de dicto beliefs to animals.

However, even on this interpretation of the intensionality test, objections have been raised. Some philosophers (Armstrong 1973; Allen & Bekoff 1997; Bermúdez 2003a, 2003b) have argued that, contrary to Davidson’s claim, there is a principled way of deciding among the alternative de dicto belief ascriptions to animals – by scientifically studying their discriminatory behaviors under various conditions and by stipulating the meanings of the terms used in our de dicto ascriptions so the they do not attribute more than what is necessary to capture the way the animal thinks. Although at present we may not be completely entitled to any one of the many de dicto belief ascriptions to animals, according to this view, there is no reason to think that we could not come to be so entitled through future empirical research on animal behavior and by the stipulation of the meanings of the terms used in our belief ascriptions. Also, it is important to mention that Bermúdez (2003a; 2003b) has developed a fairly well worked out theory of how to make de dicto ascriptions to animals that takes the practice of making such attributions to be a form of success semantics – “the idea that true beliefs are functions from desires to action that cause thinkers to behave in the ways that will satisfy their desires” (2003a, p. 65). (See Fodor 2003 for a criticism of Bermúdez’s success semantic approach.)

In addition, David Armstrong (1973) has objected that the intensionality test merely undermines our justification of de dicto belief ascriptions to animals, not de re belief ascriptions, since the latter do not aim to describe how the animal thinks but simply to identify the state of affairs the animal’s thought is about. Furthermore, Armstrong argues that it is in fact de re belief ascriptions, not de dicto belief ascriptions, that we ordinarily use to describe animal beliefs. When we say that Fido believes that the cat is up the tree, for example, our intention is simply to pick out the state of affair that Fido’s belief is about, while remaining neutral with respect to how Fido thinks about it. Roughly, what we are saying, according to Armstong, is that Fido believes a proposition of the form Rab, where ‘R’ is Fido’s relational concept that picks out the same two-place relation as our term ‘up,’ ‘a’ is Fido’s concept that refers to the same class of animals as our word ‘cat,’ and ‘b’ is Fido’s concept that refers to the same class of objects as our word ‘tree.’

ii. The Argument from Holism

One thing that Armstrong’s objection assumes is that we are at present justified in saying what objects, properties, or states of affairs in the world an animal’s belief is about. Davidson’s second argument, the argument from holism, aims to challenge this assumption. Davidson endorses a holistic principle regarding how the referents or extension of beliefs are determined. According to this principle, “[b]efore some object in, or aspect of, the world can become part of the subject matter of a belief (true or false) there must be endless true beliefs about the subject matter” (1984, p. 168). Applying this principle to the case of animals, Davidson argues that in order for us to be entitled to fix the extension of an animal’s belief, we must suppose that the animal has an endless stock of other beliefs. So, according to Davidson, to be entitled to say that Fido has a belief about a cat, we must assume that Fido has a large stock of other beliefs about cats and related things, such as that cats are three-dimensional objects that persist through various changes, that they are animals, that animals are living organisms, that cats can move freely about their environment, and so on. There is no fixed list of beliefs about cats and related items that Fido needs to possess in order to have a belief about cats, Davidson maintains, but unless Fido has a very large stock of such general beliefs, we will not be entitled to say that he has a belief about a cat as opposed to something else, such as undetached cat parts, or the surface of a cat, or a cat appearance, or a stage in the history of a cat. But in the absence of speech, Davidson claims, “there could [not] be adequate grounds for attributing the general beliefs needed for making sense of any thought” (Davidson 1985, p. 475). The upshot is that we are not, and never will be, justified even in our de re ascriptions of beliefs to animals.

One chief weakness with Davidson’s argument here is that its rests upon a radical form of holism that would appear to deny that any two human beings could have beliefs about the same things, since no two human beings ever share all (or very nearly all) the same general background beliefs on some subject. This has been taken by some philosophers as a reductio of the theory (Fodor and Lepore 1992).

iii. Davidson’s Main Argument

Davidson’s main argument against animal thought consists of the following two steps:

First, I argue that in order to have a belief, it is necessary to have the concept of belief.

Second, I argue that in order to have the concept of belief one must have language. (1985, p. 478)

Davidson concludes from these steps that since animals do not understand or speak a language, they cannot have beliefs. Davidson goes on to defend the centrality of belief, which holds that no creature can have thought or reason of any form without possessing beliefs, and concludes that animals are incapable of any form of thought or reason.

Davidson supports the first step of his main argument by pointing out what he sees as a logical connection between the possession of belief and the capacity for being surprised, and between the capacity for being surprised and possessing the concept belief. The idea, roughly, is that for any (empirical) proposition p, if one believes that p, then one should be surprised to discover that p is not the case, but to be surprised that p is not the case involves believing that one’s former belief that p was false, which, in turn, requires one to have the concept belief (as well as the concept falsity). (See Moser (1983) for a rendition of Davidson’s argument that avoids Davidson’s appeal to surprise.)

Davidson’s defense of the second step of his main argument is sketchier and more speculative. The general idea, however, appears to be as follows. If one has the concept belief and is thereby able to comprehend that one has beliefs, then one must also be able to comprehend that one’s beliefs are sometimes true and sometimes false, since beliefs are, by their nature, states capable of being true or false. However, to comprehend that one’s beliefs are true or false is to comprehend that they succeed or fail to depict the objective facts. But the only way for a creature to grasp the idea of a world of object facts, Davidson speculates, is through its ability to triangulate – that is, through its ability to compare its own beliefs with those of others. Therefore, Davidson argues, since triangulation necessarily involves the capacity of ascribing beliefs to others and this capacity, according to the intensionality test and the argument from holism (see sections 1c.i and 1c.ii. above), requires language, possessing the concept belief requires the possession of language.

A number of commentators of Davidson’s main argument have raised objections to his defense of its first step – that having beliefs requires having the concept belief. Carruthers (2008), Tye (1997) and Searle (1996), for example, all argue that having beliefs does not require having the concept belief. These philosophers agree that beliefs, by their nature, are states that are revisable in light of supporting or countervailing evidence presented to the senses but maintain that this process of belief revision does not require the creature to be aware of the process or to have the concept belief. Carruthers (2008) offers the most specific defense of this claim by developing an account of surprise that does not involve higher-order beliefs, as Davidson maintains. According to Carruthers’ account, being surprised simply involves a mechanism that is sensitive to conflicts between the contents of one’s beliefs – that is, conflicts with what one believes, not conflicts with the fact that one believes such contents. On this model, being surprised that there is no coin in one’s pocket involves having a mechanism in one’s head that takes as its input the content that there is a coin in one’s pocket (not the fact that one believes this content) and the content that there is no coin in one’s pocket (again, not the fact that one believes this content) and produces as its output a suite of reactions, such as releasing chemicals into the bloodstream that heightens alertness, widening the eyes, and orienting towards and attending to the perceived state of affairs one took as evidence that there is no coin in one’s pocket. It is one’s awareness of these changes, Carruthers argues, not one’s awareness that one’s former belief was false, as Davidson maintains, that constitutes being surprised.

Compared with the commentary on the first step of his main argument, there is little critical commentary in print on Davidson’s defense of the second step of his main argument. However, Lurz (1998) has raised the following objection. He argues that the intensionality test and the argument from holism at most show that belief attributions to nonlinguistic animals are unjustified but not that they are impossible. The fact that we routinely attribute beliefs to nonlinguistic animals shows that such attributions are quite possible. But, Lurz argues, if we can attribute beliefs to nonlinguistic animals on the basis of their nonlinguistic behavior, then there is no reason to think (at least, none provided by the intensionality test and the argument from holism) that a nonlinguistic animal could not in principle attribute beliefs to other nonlinguistic animals on the same basis. Of course, if the intensionality test and argument from holism are sound, such belief attributions would be unjustified, but this alone is irrelevant to whether it is possible for nonlinguistic animals to attribute beliefs to others and thereby engage in triangulation; for triangulation requires the capacity for belief attribution, not the capacity for justified belief attribution. Therefore, Lurz argues, if triangulation is possible without language, then Davidson has failed to prove that having the concept belief requires language. Furthermore, if some animals actually are capable of attributing beliefs to others, as some researchers (Premack & Woodruff 1978; Menzel 1974; Tschudin 2001) have suggested that chimpanzees and dolphins may be (thought such claims are considered highly controversial at present), then even if triangulation is a requirement for having beliefs, as Davidson maintains, it may turn out that some animals (e.g., chimpanzees and dolphins) actually have beliefs, contrary to what Davidson’s main argument concludes.

d. Contemporary Philosophical Arguments on Animal Reason

Although the vast majority of contemporary philosophers do not go as far as Descartes and Davidson in denying reason to animals completely, a number of them have argued for important limits on animal rationality. The arguments here are numerous and complex; so only an outline of the more influential ones is provided.

In Rationality (1964/1989), Jonathan Bennett argued that since it is impossible for animals without language to express universal beliefs (e.g., All As are Bs) and past-tensed beliefs (e.g., A was F) separately, they cannot posses either type of belief, on the grounds that what cannot be manifested separately in behavior cannot exist as distinct and separate states in the mind. A consequence of this argument is that animals cannot think or reason about matters beyond their own particular and immediate circumstances. In Linguistic Behaviour (1976), Bennett went further and argued that animals cannot draw logical inferences from their beliefs, on the grounds that if they did, they would do so for every belief that they possessed, which is absurd. According to this argument, Fido may believe that the cat is in tree, as well as believe that there is an animal in the tree, but he cannot come to have the latter belief as result of inferring it from the former.

More recently, José Bermúdez (2003a) has argued that the ability to think about thoughts (what Bermúdez calls “intentional ascent”) requires the ability to think about words in one’s natural language (what Bermúdez calls “semantic ascent”), and that since animals cannot do the latter, they cannot do the former. Bermudez’s argument that intentional ascent requires semantic ascent is, roughly, that thinking about thought involves the ability to “’to hold a thought in mind’ in such a way that can only be done if the thought is linguistically vehicled” via a natural language sentence that one understand (p. ix). The idea is that the only way for a creature to grasp and think about a thought (i.e., an abstract proposition) is by its saying, writing, or bringing to mind a concrete sentence that expresses the thought in question. Bermúdez goes on to argue that the ability to think about thoughts (propositions) is involved in a wide variety of types of reasoning, from thinking about and reasoning with truth-functional, temporal, modal, and quantified propositions, to thinking and reasoning about one’s own and others’ propositional attitudes (e.g., beliefs and desires). Bermúdez concludes that since animals do no think about words or sentences in a natural language, their thinking and reasoning are restricted to observable states of affairs in their environment. However, see Lurz (2007) for critical comment on Bermúdez’s argument here.

Finally, John Searle (1994) has argued that since animals lack certain linguistic abilities, they cannot think or reasons about institutional facts (e.g., facts about money or marriages), facts about the distant past (e.g., facts about matters before their birth), logically complex facts (e.g., subjunctive facts or facts that involve mixed quantifies), or facts that can only be represented via some symbolic system (e.g., facts pertaining to the days of the week). In addition, and more interesting, Searle (2001) has argued that since animals cannot perform certain speech acts such as asserting, they cannot have desire-independent reasons for action. According to this argument, animals act only for the sake of satisfying some non-rationally assessable desire (e.g., the satisfaction of hunger) and never out of a sense of commitment. Consequently, if acts of courage, fidelity, loyalty, and parental commitment involve desire-independent reasons for action, as they arguably do, then on Searle’s argument here, no animal is or can be courageous, faithful, loyal, or a committed parent.

e. Contemporary Philosophical Arguments for Animal Thought and Reason

There are four types of arguments in contemporary philosophy for animal thought and reason. The first is the argument from the intentional systems theory championed by Daniel Dennett (1987, 1995, 1997). The second is the argument from common-sense functionalism championed by (among others) Jerry Fodor (1987), Stephen Stich (1979) and Peter Carruthers (2004). The third is the argument from biological naturalism, championed by John Searle (1994). And the fourth is the argument from science championed by (among others) Allen and Bekoff (1997) and Bermúdez (2003a).

i. The Intentional Systems Theory Argument

The intentional systems theory consists of two general ideas. The first is that our concepts of intentional states, such as our concepts belief, desire, and perceiving, are theoretical concepts whose identity and existence are determined by a common-sense psychological theory or folk-psychology. Folk psychology is a set of general principles that state that subjects, on the assumption that they are rational, tend to believe what they perceive, tend to draw obvious logical inferences from their beliefs, and tend act so as to satisfy their desires given what they believe. In many cases, we apply our folk psychology to animals to predict and make sense of their behaviors. When we do, we view animals as intentional systems and take up, what Dennett (1987) calls, the intentional stance toward them. The second important idea of the intentional systems theory is its instrumentalist interpretation of folk psychology. On the instrumentalist interpretation, what it is for a creature to have intentional states is for its behaviors to be well predicted and explained by the principles of folk psychology. Nothing more is required. There need not be anything inside the creatures’ brain or body, for instance, that corresponds to or has structural or functional features similar to the intentional state concepts employed in our folk psychology. Our intentional state concepts, on the instrumentalist reading, do not aim to refer to real, concrete internal states of subjects but to abstract entities that are merely useful constructs for predicting and explaining various behaviors (much like centers of gravity used in mechanics). Therefore, according to the intentional systems theory argument, the fact that much of animal behavior is usefully predicted and explained from the intentional stance makes animals genuine thinkers and reasoners.

There are two general types of objections raised against the intentional systems theory argument. First, some have argued (Searle 1983) that our intentional state concepts are not theoretical concepts, since intentional states are experienced and, hence, our concepts of them are independent of our having any theory about them. Second, some (Braddon-Mitchell & Jackson 2007) have objected to the intentional systems theory’s commitment to instrumentalism, arguing that on such an interpretation of folk psychology, even lowly thermostats, laptop computers, and Blockheaded robots have beliefs and desires, since it is useful to predict and explain behaviors of such objects from the intentional stance.

ii. The Argument from Common-Sense Functionalism

Similar to the intentional systems theory, common-sense functionalism holds that our intentional state concepts are theoretical concepts that belong to and are determined by our folk psychology. Unlike the intentional systems theory, however, common-sense functionalism takes a realist interpretation of folk psychology. (In addition, many common-sense functionalists reject the rationality assumption that the intentional systems theory places on folk psychology (Fodor 1987, 1991).) On the realist interpretation, for a subject to have intentional states is for the subject to have in his brain a variety of discrete internal states that play the causal roles and have the internal structures that our intentional state concepts describe. According to this view, if Fido believes that the cat is up the tree, then he has in his brain an individual state, s, that plays the causal role that beliefs play according to our folk psychology, and s has an internal structure similar to the ‘that’-clause used to specify its content – that is, s has the structure Rxy where ‘R’ represents the two-place relation up, ‘x’ represents the cat, and ‘y’ represents the tree. Since the internal state s is seen as having an internal structure similar to the sentence ‘the cat is up the tree,’ common-sense functionalism is often taken to support the view that thinking involves an internal language or language of thought (Fodor 1975). It is then argued that since animal behavior is successfully predicted and explained by our folk psychology, there is defeasible grounds for supposing that animals actually have such internal states in their heads (Fodor 1987; Stich 1979; Carruthers 2004).

Two problems are typically raised regarding the argument from common-sense functionalism. Some (Stalnaker 1999) have objected that if, as common-sense functionalism claims, our ascriptions of intentional states to animals commit us to thinking that the animals have in their heads states that have the same representational structure as the ‘that’-clauses we use to specify their contents, then intentional ascriptions to animals (and to ourselves) would be a far more speculative practice than it actually is. The objection here does not deny that animals actually have such representational structures in their heads, it simply denies that that is what we are saying or thinking when we ascribe intentional states to them. Others (Camp, forthcoming) accept the common-sense functionalist account of intentional state concepts but have argued, on the basis of Evan’s (1982) generality constraint principle, that few animals have the sorts of structured representational states in their heads that folk psychology describes them as having. If Fido’s thoughts are structured in the way that common-sense functionalism claims, the objection runs, then if Fido is able to think that he is chasing a cat, then he must also be capable of thinking that a cat is chasing him, but, it is argued, this may be a thought that is completely unthinkable by Fido. However, see Carruthers (2009) and Tetzlaff and Rey (2009) for important objections to this type of argument.

iii. The Argument from Biological Naturalism

Biological naturalism is the theory, championed by John Searle (1983, 1992), that holds that our concepts of intentional states are concepts of experienced subjective states. The concept belief, for example, is the concept of an experienced, conscious state that has truth conditions and world-to-mind direction of fit; whereas, our concept desires is the concept of an experienced, conscious state that has satisfaction conditions and mind-to-world direction of fit. Intentional states, according to this theory, are irreducibly subjective states that are caused by low-level biochemical states of the brain in virtue of their causal structures, not in virtue of their functional or causal roles, or, if they have such, their representational structures. According to biological naturalism, if Fido believes that the cat is in the tree, then he has in his brain a low-level biochemical state, s, that, in virtue of its unique causal structure, causes Fido to have a subjective experience that has a world-to-mind direction of fit and is true if and only if the cat is in the tree.

Searle argues that there are two main reasons why we find it irresistible to suppose that animals have intentional states, as biological naturalism conceives them. First, many animals have perceptual organs (e.g., eyes, ears, mouths, and skin) that we see as similar to our own and which, we assume, operate according to similar physiological principles. Since we know in our own case that the stimulation of our perceptual organs leads to certain physiological processes which cause us to have certain perceptual experiences, we reason, from the principle of similar cause-similar effect, that the stimulation of perceptual organs in animals leads to similar physiological processes which cause them to have similar perceptual experiences. The behavior of animals, Searle repeatedly stresses, is by itself irrelevant to why we think animals have perceptual experiences; it is only relevant if we take the behavior to be caused by the stimulation of perceptual organs and underlying physiological processes relevantly similar to our own. This argument, of course, would only account for why we think that animals have perceptual experiences, not why we think that they have beliefs, desires, and other intentional states that are only distantly related to the stimulation of sensory organs. So Searle adds that the second reason we find it irresistible that animals have intentional states is that we cannot make sense of their behaviors otherwise. To make sense of why Fido is still barking up the tree when the cat is long out of sight, for example, we must suppose that Fido continues to want to catch the cat and continues to think that the cat is up the tree.

There are two main problems with Searle’s argument for animal thought and reason. First, according to biological naturalism, animals have intentional states solely in virtue of their having brain states that are relevantly similar in causal structure to those in human beings which cause us to have intentional states. But this raises the question: how are we to determine whether the brain states of animals are relevantly similar to our own? They will not be exactly similar, since animal brains and human brains are different. Suppose, for example, scientists discover that a certain type of electro-chemical process (XYZ) in human brains is necessary and sufficient for intentional states in us, and that an electro-chemical process (PDQ) similar to XYZ occurs in animal brains. Is PDQ similar enough to XYZ to produce intentional states in animals? Well, suppose PDQ produces behaviors in animals that are similar to those that XYZ produces in humans. Would that show that PDQ is enough like XYZ to produce intentional states in animals? No, says Searle, for unless those behaviors are produced by relevantly similar physiological processes they are simply irrelevant to whether the animal has intentional states. But that is precisely what we are trying to determine here, of course. It would appears that the only way to determine whether PDQ is similar enough to XYZ, on biological naturalism, is if we humans could temporarily exchange our brains for those of animals and see whether PDQ produces intentional states in us. This, of course, is impossible. And so it would appear that the question of whether animals have intentional states is, on biological naturalism, unknowable in principle.

Finally, Searle’s explanation for why we find it irresistible to ascribe perceptual experiences to animals seems questionable in some cases. If Searle’s explanation were correct, then most ordinary individuals should not find it at all compelling, for example, to ascribe auditory experiences (i.e., hearing) to birds, or tactile experiences (i.e., feelings of pressures, pain, or temperature) to fish or armadillos, since most ordinary individuals do not see anything on birds’ heads that looks like ears or on the outer surface of fish or armadillos that looks like skin.

iv. The Argument from Science

Why should we believe that colds are caused by viruses and not by drastic changes in weather, as many folk had (and still do) believe? A reasonable answer is that our best scientific theory of the causes of colds is in terms of viruses, commonsense notwithstanding. Sometimes, of course, science and commonsense agree, and when they do, commonsense can be said to be vindicated by science. In either case, it is science that ultimately determines what should (and should not) be believed. This type of argument, sometimes called the argument from science, has been used to justify the claim that animals have thought, reason, consciousness, and other folk-psychological states of mind (see Allen & Bekoff 1997; Bermúdez 2003a). In the past thirty years or so, due in large measure to the demise of radical behaviorism and the birth of cognitivism in psychology, as well as from the influential writings of ethologist Donald Griffin (1976, 1984, 2001), scientists from various fields have found it increasingly useful to propose, test, and ultimately accept hypotheses about the causes of animal behavior in explicitly folk-psychological terms. It is quite common these days to see scientific articles on whether, for example, animals have conscious experiences such as pain, seeing and (even) joy (Griffin & Speck 2004; Panksepp & Burgdorf 2003), on whether scrub jays have desires, and beliefs, and can recollect their pasts (Clayton et al. 2006), on whether primates understand that other animals know, see, and hear (Hare et al. 2000; Hare et al. 2001; Santos et al. 2006), on whether primates make judgments about their own states of knowledge and ignorance (Hampton et al. 2004; Smith et al. 2003), and so on. According to the argument, since scientists are finding it useful to test and accept hypothesis about animal behavior in folk-psychological terms, we are justified in believing that animals have such states of mind.

Not everyone has found the argument from science here convincing, however. The chief concern is whether explanations of animal behavior in folk-psychological terms are, as the argument assumes, scientifically respectable (see Kennedy 1992). There are two features of scientific explanations of animal behavior that appear to count against their being so. First, scientific explanations of animal behavior are causal explanations in terms of concrete internal states of the animal, but on some models of folk-psychology, such as Dennett’s intentional systems theory (see 1.e.i. above), folk-psychological explanations are neither causal explanations nor imply anything about the internal states of the animal. Second, scientific explanations of animal behavior are objective in that there is typically a general agreement among researchers in the field on what would count in favor of or against the explanation; however, it has been argued that since the only generally agreed upon indicators of consciousness are verbal reports of the subject, explanations of animal behavior in terms of consciousness are unscientific (see Clayton et al. 2006, p. 206).

One standard type of reply to these objections has been to adopt a common-sense functionalist model of folk-psychology (see 1e.ii above) which interprets folk-psychological explanations as imputing causally efficacious internal states while denying that these explanations imply anything about the consciousness of the internal states. (This seems to be the approach that Clayton et al. (2006) take in their explanation of the behaviors of scrub jays in terms of “episodic-like” memories, which are episodic memories minus consciousness.) This, of course, raises the vexing issue of whether our folk-psychological concepts, such as belief, desire, intention, seeing, etc. imply consciousness (see Carruthers 2005; Lurz 2002a; Searle 1992; Stich 1979). Others have responded to above objections by developing non-subjective measures for consciousness that could be applied to animals (and humans) incapable of verbal reports (Dretske 2006). And still others have proposed objective measures of consciousness in animals by appealing to the communicative signals of animals as non-verbal reports of the presence of conscious experiences (Griffin 1976, 1984, 2001).

2. The Problems of Animal Consciousness

It is generally accepted that most (if not all) types of mental states can be either conscious or unconscious, and that unconscious mental states can have effects on behavior that are not altogether dissimilar from those of their conscious counterparts. It is quite common, for example, for one to have a belief (e.g., that one’s keys are in one’s jacket pocket) and a desire (e.g., to locate one’s keys) that are responsible for some behavior (e.g., reaching into one’s jacket pocket as one approaches one’s apartment) even though at the time of the behavior (and beforehand) one’s mind is preoccupied with matters completely unrelated to one’s belief or desire. Similarly, scientists have shown through various masking experiments and the like that our behaviors are often influenced by stimuli that are perceived below the level of consciousness (Marcel 1983). Also some philosophers have argued that even pains and other bodily sensations can be unconscious, such as when one continues to limp from a pain in one’s leg though at the time one is preoccupied with other matters and is not attending to the pain (Tye 1995).

Given this distinction between conscious and unconscious mental states, the question arises whether the mental states of animals are or can be conscious. It should be noted that this question not only has theoretical import but moral and practical import, as well. For arguably the fact that conscious pains and experiences feel a certain way to their subjects makes them morally relevant conditions, and it is, therefore, of moral and practical concern to determine whether the mental states of animals are conscious (Carruthers 1992). Of course, as with the question of animal thought and reason, the answer to this question depends in large part on what one takes consciousness to be. There are two general philosophical approaches to consciousness – typically referred to as first-order and higher-order theories – that have played a prominent role in the debate over the status of animal consciousness. These two approaches and their relevance to the question of conscious states in animals are described below.

a. Higher-Order Theories of Consciousness

Higher-order theories start with the common assumption that conscious mental states are states of which one is higher-order aware, and unconscious mental states are states of which one is not higher-order aware. The theories diverge, however, over what is involved in being higher-order aware of one’s mental states.

i. Inner-Sense Theories

Inner-sense theories take a subject’s higher-order awareness to be a type of perceptual awareness, akin to seeing, that is directed inwardly toward the mind as opposed to outwardly toward the world (Lycan 1996; Armstrong 1997). Since higher-order awareness is a species of perceptual awareness, on this view, it is not usually taken to require the capacity for higher-order thought or the possession of mental-state concepts. A subject need not be able to think that he is in pain or have the concepts I or pain, for example, in order for him to be higher-order aware of his pain. On the inner-sense theory, then, the mental states of animals will be conscious just in case they are higher-order aware of them by means of an inner perception.

Some inner-sense theorists have argued that since higher-order awareness does not require higher-order thought or the possession of mental-state concepts, it is quite consistent with what we know about animal behavior and brains that many animals may have such an awareness of their own mental states. Furthermore, there are recent studies in comparative psychology (Smith et al. 2003; Hampton et al. 2004) that suggest that monkeys, apes and dolphins actually have the capacity to be higher-order aware of their own states of certainty, memory, and knowledge. However, the results of these studies have not gone unchallenged (see Carruthers 2008).

The chief problem with inner-sense theories, however, is not so much their account of animal consciousness but their account of higher-order awareness. Some (Rosenthal 1986; Shoemaker 1996) have argued against a perceptual account of higher-order awareness on the grounds that (i) there is no dedicated perceptual organ in the brain for such a perception as there is for external perception; (ii) there is no distinct phenomenology associated with higher-order awareness as there is for all other types of perceptual modalities; and (iii) it is impossible to reposition oneself in relation to one’s mental states so as to get a better perception of them as one can do in the case of perception of external objects. And still others (Lurz 2003) have objected that the inner-sense theory cannot explain how concept-involving mental states, such as beliefs and desires, can be conscious, since to be aware of such states would require being aware of their conceptual contents, which cannot be done by way of a perceptual awareness that is not itself concept-involving.

ii. Higher-Order Thought Theories

Problems such as these have led a number of higher-order theorists (Rosenthal 1986; Carruthers 2000) to embrace some version or other of the higher-order thought theory. According to this theory, a mental state is conscious just in case one has (or is disposed to have) the higher-order thought that one is in such a mental state. Animals will have conscious mental states, on this theory, if and only if that they are capable of higher-order thoughts about themselves as having mental states. The question of animal consciousness, then, becomes the question of whether animals are capable of such higher-order thought.

A number of philosophers have argued that animals are incapable of such thought. Some have argued that since higher-order thoughts require the possession of the first-person I-concept, it is unlikely that animals are capable of having them. The selves of animals, the argument runs, are selves that experience numerous mental states at any one moment in time and that persist through various changes to their mental states. Thus, if an animal possessed the I-concept, it must be capable of understanding itself as such an entity – that is, it must be capable of thinking not only, I am currently in pain, for example, but I am currently in pain, am seeing, am hearing, am smelling, as well as be capable of thinking I was in such-and-such mental states but am not now. However, such thoughts appear to involve the mental equivalent of pronominal reference and past-tensed thoughts, both of which, it is argued, are impossible without language (see Quine 1995; Bermúdez 2003a; Bennett 1964, 1966, 1988).

Various objections have been raised against this argument on behalf of the higher-order theory and animal consciousness. Gennaro (2004, 2009) argues that that the I-concept involved in higher-order thoughts need be no more sophisticated than the concept this particular body or the concept experiencer of mental states, and that the results of various self-recognition studies with apes, dolphins and elephants, as well as the results of a number of episodic memory tests with scrub jays, suggest that many animals possess such minimal I-concepts (Parker et al. 1994; Clayton et al., 2003). Lurz (1999) goes further and argues that insofar as higher-order thoughts confer consciousness on mental states, they need not involve any I-concept at all. The idea here is that just as one can be aware that it is raining, where the ‘it’ here is not used to express one’s concept of a thing or a subject – for there is no thing or subject that is raining -- an animal can be aware that it hurts or thinks that p, where the ‘it’ here does not express a concept of a thing or a subject that is thought to possess pain or to think that p. Animals, on this view, are thought to conceive of their mental states as we conceive of rain and snow – that is, as subject-less features placed at a time (see Strawson (1959) and Proust (2009) for similar arguments).

The most common argument against animals possessing higher-order thought, however, is that such thoughts requires linguistic capabilities and mental-state concepts that animals do not possess. Dennett (1991), for example, argues that the ability to say what mental state one is in is the very basis of one’s having the higher-order thought that one is in such mental state, and not the other way round. To think otherwise, Dennett argues, is to commit oneself to an objectionable Cartesian theater view of the mind. According to Dennett’s argument, since animals are incapable of saying what they are feeling or thinking, they are incapable of thinking that they are feeling or thinking. In reply, Carruthers (1996) has argued that there is a way of understand higher-order thoughts that is not tied to linguistic expression of any kind or committed to a Cartesian theater view of the mind.

In a somewhat similar vein of thought to Dennett’s, Davidson (1984, 1985) and Bermúdez (2003a) argue, although on different grounds, that since animals are incapable of speaking and interpreting a natural language, they cannot possess mental-state concepts for propositional attitudes and, therefore, cannot have higher-order thoughts about their own or others propositional attitudes (see sections 1c and 1d.iii above). This alone, of course, is not sufficient to prove that animals are incapable of higher-order thoughts about non-propositional mental states, such as bodily sensations and perceptual experiences. However, some have gone further and argued that animals are incapable of possessing any type of mental-state concept and, therefore, any type of higher-order thought. The argument for this view generally consist of the following two main premises: (1) if animals possess mental-state concepts, then they must have the capacity to apply these concepts to themselves as well as to other animals; and (2) animals have been shown to perform poorly in some important experiments designed to test whether they can apply mental-state concepts to other animals.

Premise (1) of this argument is sometimes supported (Seager 2004) by an appeal to Evan’s generality constraint (see section 1e.ii above); roughly, the argument runs, if an animal can think, for example, I am in pain, and can think of another animal that, for example, he walks, then the animal in question must be capable of thinking of another animal, he is pain, as well as be capable of thinking of himself, I walk. Others, however, have supported premise (1) on evolutionary grounds, arguing that animals would not have evolved the capacity to think with mental-state concepts unless their doing so was of some selective advantage, and the only selective advantage of thinking with mental-state concepts is its use in anticipating and manipulating other animals’ behaviors (Humphrey 1976). Premise (2) of this argument has been supported mainly by the results of a series of experiments conducted by Povinelli and colleagues (see Povinelli & Vonk 2004) which appear to show that chimpanzees are incapable of discriminating between seeing and not seeing in other subjects.

Various objections have been raised against such defenses of premises (1) and (2). Gennaro (2009), for example, has argued against the defense of premise (1) based on Evan’s generality constraint. Others have argued that, contrary to the evolutionary defense given for premise (1), the principal selective advantage of thinking with mental-state concepts is its use in recognizing and correcting errors in one’s own thinking, and that the results of various meta-cognition studies have shown that various animals are capable of reflecting upon and improving their pattern of thinking (Smith et al., 2003). (However, see Carruthers (2008) for a critique of such higher-order interpretations of these studies.) And with respect to premise (2), others have argued that, contrary to Povinelli’s interpretation, chimpanzees fail such discrimination tasks not because they are unable to attribute mental states to others but because the experimental tasks are unnatural and confusing for the animals, and that when the experimental tasks are more suitable and natural, such as those used in competitive paradigms (Hare et al. 2000; Hare et al. 2001; Santos et al. 2006), the animals show signs of mental-state attribution. However, see Penn and Povinelli (2007) for challenges to the supposed successes of mental-state attributions by animals in these new experimental protocols and for suggestions on how to improve experimental methods used in testing mental-state attributions in animals.

b. First-Order Theories

According to first-order theories, conscious mental states are those that make one conscious of things or facts in the external environment (Evans 1982; Tye 1995; Dretske 1995). Mental states are not conscious because one is higher-order aware of them but because the states themselves make one aware of the external world. Unconscious mental states, therefore, are mental states that fail to make one conscious of things or facts in the environment -- although, they may have various effects on one’s behavior. Furthermore, mental states that make subjects conscious of things or facts in the environment do so, according to first-order theories, in virtue of their effecting, or being poised to effect, subjects’ belief-forming system. So, for example, one’s current perception of the computer screen is conscious, on such theories, because it causes, or is poised to cause, one to believe that there is a computer screen before one; whereas, those perceptual states that are involved in subliminal perception, for instance, are not conscious because they do not cause, nor are poised to cause, subjects to form beliefs about the environment.

First-order theorists argue (Tye 1997; Dretske 1995) that many varieties of animals, from fish to bees to chimpanzees, form beliefs about their environment based upon their perceptional states and bodily sensations and, therefore, enjoy conscious perceptual states and bodily sensations. Additional virtues of first-order theories, it is argued, are the fact that they offer a more parsimonious account of consciousness than higher-order theories, since they do not require higher-order awareness for consciousness, and that they provide a more plausible account of animal consciousness than higher-order theories, since they ascribe consciousness to animals that we intuitively believe to possess conscious perceptual states (e.g., bats and mice) but do not intuitively believe to possess higher-order awareness.

It has been argued (Lurz 2004, 2006), however, that first-order theories are at their best when explaining the consciousness of perceptual states and bodily sensations but have difficultly explaining the consciousness of beliefs and desires. Most first-order theorists have responded to this problem by endorsing a higher-order thought theory of consciousness for such mental states (Tye 1997; Dretske 2000, p. 188). On such a hybrid view, beliefs and desires are conscious in virtue of having higher-order thoughts about them, while perceptual states and bodily sensations are conscious in virtue of their being poised to make an impact on one’s belief-forming system. This hybrid view faces two important problems, however. First, on such a view, few, if any, animals would be capable of conscious beliefs and desires, since it seems implausible, for various reasons, to suppose that many animals are capable of higher-order thoughts about their own beliefs and desires. And yet it has been argued (Lurz 2002b) that there is intuitively compelling grounds for thinking that many animals are capable of conscious beliefs and desires, since their behaviors are quite often predictable and explainable in terms of the concepts belief and desire of our folk psychology, which is a set of laws about the causal properties and interactions of conscious beliefs and desires (or, at the very least, a set of laws about the causal properties and interactions of beliefs and desires that are apt to be conscious (Stich 1978)). However, see Carruthers (2005) for a reply to this argument.

The second problem for the hybrid view is that on its most plausible rendition it would ascribe consciousness to the same limited class of animals as higher-order thought theory and, thereby, provide no more of an intuitively plausible account of animal consciousness than its main competitor. For it seems intuitively plausible to suppose that a perceptual state or bodily sensation will be conscious only if it effects, or is poised to effect, a subject’s conscious belief-forming system. If it were discovered, for example, that the perceptual states involved in subliminal perception (or blindsight) caused subjects to form unconscious beliefs about the environment, no one but the most committed first-order theorist would conclude from this alone that these perceptual states were, after all, conscious. But if perceptual states and bodily sensations are conscious only insofar as they effect (or are poised to effect) a subject’s conscious belief-forming system, and conscious beliefs, on the hybrid view, require higher-order thought, then to possess conscious perceptions and bodily sensations, an animal would have to be, as higher-order thought theories maintain, capable of higher-order thought. What appears to be need here in order to save first-order theories from this problem is a first-order account of conscious beliefs and desires. See Lurz (2006) for a sketch of such an account.

3. Other Issues

There are many other important issues in the philosophy of animal minds in addition to those directly related to the nature and scope of animal thought, reason, and consciousness. Due to considerations of length, however, only a brief list of such issues with reference to a few relevant and important sources is provided.

The nature and extent of animal emotions has been, and continues to be, an important issue in the philosophy of animal minds (see Nussbaum 2001; Roberts 1996, 2009: Griffiths 1997), as well as the nature and extent of propositional knowledge in animals (see Korblith 2002). Philosophers have also been particularly interested in the philosophical foundations and the methodological principles, such as Lloyd Morgan’s canon, employed in the various sciences that study animal cognition and consciousness (see Bekoff et al. 2002; Allen and Bekoff 1997; Fitzpatrick 2007, 2009; Sober 1998, 2001a, 2001b, 2005). Philosophers have also been interested in the nature and justification of the practice of anthropomorphism by scientist and lay folk (Mitchell at al.1997; Bekoff & Jamieson 1996; Datson & Mitman 2005). And finally, there is a rich history of philosophical thought on animal minds dating back to the earliest stages of philosophy and, therefore, there has been, and continues to be, philosophical interest and issues related to the history of the philosophy of animal minds (see Sorabji, 1993; Wilson, 1995; DeGrazia, 1994).


4. References and Further Reading


a. References

Allen, C. & Bekoff, M. (1997). Species of Mind. Cambridge, MA: MIT Press.

Armstrong, D. (1973). Belief, Truth and Knowledge. Cambridge: Cambridge University Press.

Armstrong. D. (1997). What Is Consciousness? In N. Block, O. Flanagan & G. Güzledere (Eds.) The Nature of Consciousness: Philosophical Debates. Cambridge, Mass.: MIT Press.

Beisecker, D. (2002). Some More Thoughts About Thought and Talk: Davidson and Fellows on Animal Belief. Philosophy 77: 115-124.

Bekoff, M. & Jamieson, D. (1996). Readings in Animal Cognition. Cambridge, Mass.: MIT Press.

Bekoff, M., Allen, C. & Burghardt, G. (2002). The Cognitive Animal: Empirical and Theoretical Perspectives on Animal Cognition. Cambridge, Mass.: MIT Press.

Bennett, J. (1964/1989). Rationality: An Essay Towards and Analysis. Indianapolis: Hackett.

Bennett, J. (1966). Kant’s Analytic. Cambridge: Cambridge University Press.

Bennett, J. (1976). Linguistic Behaviour. Indianapolis: Hackett.

Bennett, J. (1988). Thoughtful Brutes. Proceedings and Addresses of the American Philosophical Association 62: 197-210.

Bermúdez, J. L. (2003a). Thinking Without Words. Oxford: Oxford University Press.

Bermúdez, J. L. (2003b). Ascribing Thoughts to Non-linguistic Creatures. Facta Philosophica 5: 313-334.

Boden, M. A. (1984). Animal Perception from an Artificial Intelligence Viewpoint. In C. Hookway (Ed.) Minds, Machines and Evolution. Cambridge: Cambridge University Press.

Braddon-Mitchell, D. & Jackson, F. (2007). Philosophy of Mind and Cognition: An Introduction (2nd edition). Oxford: Blackwell Publishing.

Camp, E. (forthcoming). Putting Thoughts to Work: Concepts, Stimulus Independence, and the Generality Constraint. Philosophy and Phenomenological Research.

Carruthers, P. (1992). The Animal Issue: Moral Theory in Practice. Cambridge: Cambridge University Press.

Carruthers, P. (1996). Language, Thought and Consciousness. Cambridge: Cambridge University Press.

Carruthers, P. (2000) Phenomenal Consciousness: A naturalistic Theory. Cambridge: Cambridge University Press.

Carruthers, P. (2004). On Being Simple Minded. American Philosophical Quarterly 41: 205-220.

Carruthers, P. (2005). Why the Question of Animal Consciousness Might Not Matter Very Much. Philosophical Psychology 17: 83-102.

Carruthers, P. (2006). The Architecture of the Mind. Oxford: Oxford University Press.

Carruthers, P. (2008). Meta-Cognition in Animals: A Skeptical Look. Mind and Language 23: 58-89.

Carruthers, P. (2009). Invertebrate concepts confront the Generality Constraint (and win). In R. Lurz (Ed.) Philosophy of Animal Minds. Cambridge: Cambridge University press.

Cottingham, J. (1978). A Brute to the Brutes?: Descartes Treatment of Animals. Philosophy 53: 551-561.

Clayton, N., Bussey, N. & Dickinson, A. (2003). Can Animals Recall the Past and Plan for the Future? Nature Reviews of Neuroscience 4: 685-691.

Clayton, N., Emery, N. & Dickinson, A. (2006). The Rationality of Animal Memory: Complex Caching Strategies of Western Scrub Jays. In S. Hurley and M. Nudds (Eds.) Rational Animals? Oxford: Oxford University Press.

Daston, L. & Mitman, G. (2005). Thinking With Animals: New Perspectives on Anthropomorphism. New York: Columbia University Press.

Davidson, D. (1984). Thought and Talk. In Inquiries into Truth and Interpretation (pp. 155-179). Oxford: Clarendon Press.

Davidson, D. (1985). Rational Animals. In E. Lepore & B. McLaughlin (Eds.) Actions and Events: Perspectives on the Philosophy of Donald Davidson. New York: Basil Blackwell.

Davidson, D. (1997). The Emergence of Thought. Erkenntnis 51: 7-17.

DeGrazia, D. (1994). Wittgenstein and the Mental Life of Animals. History of Philosophy Quarterly 11: 121-137.

Dennett, D. (1987) The Intentional Stance. Cambridge, MA: MIT Press.

Dennett, D. (1991). Consciousness Explained. Boston: Little, Brown and Company.

Dennett, D. (1995). Do Animals Have Beliefs? In H. Roitblat (Ed.) Comparative Approaches to Cognitive Science. Cambridge, MA: MIT Press

Dennett, D. (1997) Kinds of Minds: Towards an Understanding of Consciousness New York: Basic Books (Science Masters Series).

Descartes, R. (1637/1988). Discourse on the Method. In Cottingham, Stoothoff, and Murdoch (Trans.) Descartes: Selected Philosophical Writings. Cambridge: Cambridge University Press.

Descartes, R. (1649/1970). Letter to Henry More (5 February 1649). In A. Kenny (Trans.) Philosophical Letters. Oxford: Clarendon Press.

Dretske, F. (1988). Explaining Behavior: Reasons in a World of Causes. Cambridge, Mass.: MIT Press.

Dretske, F. (1995) Naturalizing the Mind. Cambridge, MA: MIT Press.

Dretske. F. (2000). Perception, Knowledge and Belief. Cambridge: Cambridge University Press.

Dretske, F. (2006). Perception without Awareness. In T. Gendler & J. Hawthorne (Eds.) Perceptual Experience. Oxford: Oxford University Press

Dummett, M. (1993). The Origins of Analytic Philosophy. London: Duckworth.

Evans, G. (1982). The Varieties of Reference. Oxford: Clarendon Press.

Fellows, R. (2000). Animal Belief. Philosophy 75: 587-598.

Fitzpatrick, S. (2007). Doing Away with Morgan’s Canon. Mind and Language.

Fitzpatrick, S. (2009). Simplicity and Methodology in Animal Psychology: A Case Study. In R. Lurz (Ed.) The Philosophy of Animal Minds. Cambridge: Cambridge University Press.

Fodor, J. (1975). The Language of Thought.

Fodor, J. (1987). Psychosemantics: The Problem of Meaning in Philosophy of Mind. Cambridge, Mass.: MIT Press.

Fodor, J. (1991). A Theory of Content and Other Essays. Cambridge, Mass.: MIT Press.

Fodor, J. & Lepore, E. (1992). Holism: A Shopper’s Guide. Oxford: Blackwell.

Fodor, J. (2003). More Peanuts. London Review of Books 25.

Gennaro, R. (2004). Higher-order thoughts, animal consciousness, and misrepresentation: A reply to Carruthers and Levine. In R. Gennaro (Ed.) Higher-Order Theories of Consciousness. Amsterdam & Philadelphia: John Benjamins.

Gennaro, R. (2009). Animals, Consciousness, and I-thoughts. In R. Lurz (Ed.) The Philosophy of Animal Minds. Cambridge: Cambridge University Press.

Giurfa, M., Zhang, S., Jenett, A., Menzel, R. & Srinivasan, M. (2001). The Concept of ‘Sameness’ and ‘Difference’ in an Insect. Nature 410: 930-933.

Glock, H. (2000). Animals, Thoughts and Concepts. Synthese 123: 35-64.

Griffin, D. (1976). The Question of Animal Awareness. New York: Rockefeller University Press.

Griffin, D. (1984). Animal Thinking. Cambridge, MA: Harvard University Press.

Griffin, D. (2001). Animal Minds: Beyond Cognition to Consciousness. Chicago: Chicago University Press.

Griffin, D. & Speck, G. (2007). New Evidence of Animal Consciousness. Animal Cognition 7:5-18.

Griffiths, P. (1997). What Emotions Really Are: The Problem of Psychological Categories. Chicago: University of Chicago Press.

Hare, B., Call, J., Agnetta, B. & Tomasello, M. (2000) Chimpanzees Know what Conspecifics Do and Do Not See. Animal Behavior 59: 771-785.

Hare, B. Call, J. & Tomasello, M. (2001). Do Chimpanzees Know What Conspecifics Do and Do Not See? Animal Behavior 59:771-785.

Hauser, M. (2000). Wild Minds. New York: Henry Holt and Co.

Hauser, M., Chomsky, N. & Fitch, W. T. (2002). The Faculty of Language: What Is It, Who Has It, and How Did It Evolve? Science 298: 1569-1579.

Hampton, R., Zivin, A., & Murray, E. (2004). Rhesus Monkeys (Macaca mulatta) Discriminate Between Knowing and not Knowing and Collect Information as Needed Before Acting. Animal Cognition, 7, 239-246.

Heinrich, B. (2000). Testing Insight in Ravens. In C. Heyes & L. Huber (Eds.) The Evolution of Cognition. Cambridge, Mass: MIT Press.

Hume, D. (1739/1978). A Treatise of Human Nature. Edited by P. H. Nidditch, 2nd Ed. Oxford: Oxford University Press.

Humphrey, N. (1976). The Social Function of Intellect. In P. P. G. Bateson & R. A. Hinde (Eds.) Growing Points in Ethology. Cambridge: Cambridge University Press.

Hurley, S. & Nudds, M. (2006). Rational Animals? Oxford: Oxford University Press.

Kennedy, J. (1992). The New Anthropomorphism. Cambridge: Cambridge University Press.

Köhler, W. (1925). The Mentality of Apes. London: Routledge and Kegan Paul.

Kornblith, H. (2002). Knowledge and its Place in Nature. Oxford: Oxford University Press.

Lurz, R. (1998). Animal Minds: The Possibility of Second-Order Beliefs in Non- Linguistic Animals. (Doctoral dissertation Temple University, 1998). Dissertation Abstracts International, 59, no. 03A.

Lurz, R. (1999). Animal Consciousness. Journal of Philosophical Research 24: 149-168.

Lurz, R. (2002a). Reducing Consciousness by Making it HOT: A Commentary on Carruthers’ Phenomenal Consciousness, Psyche 8.

Lurz, R. (2002b). Neither HOT nor COLD: An Alternative Account of Consciousness. Psyche 9.

Lurz, R. (2003). Advancing the Debate Between HOT and FO Theories of Consciousness. Journal of Philosophical Research 28: 23-44.

Lurz, R. (2004). Either FOR or HOR: A False Dichotomy, in R. Gennaro (Ed.) Higher- Order Theories of Consciousness, John Benjamins, Amsterdam, 2004, pp. 226- 54.

Lurz, R. (2007). In Defense of Wordless Thoughts about Thoughts. Mind and Language 22 : 270-296.

Lurz. R. (2006). Conscious Beliefs and Desires: A Same-Order Approach, in U. Kriegel and K. Williford (Eds.) Self-Representational Approaches to Consciousness, MIT Press.

Lurz, R. (2009). Philosophy of Animal Minds : New Essays on Animal Thought and Consciousness. Cambridge : Cambridge University Press.

Lycan, W. (1996). Consciousness and Experience. Cambridge, Mass.: MIT Press.

Malcolm, N. (1977). Thoughtless Brutes. In Thought and Knowledge. Ithaca: Cornell University Press.

Marcel , A. (1983). Conscious and unconscious perception. Cognitive Psychology, 15: 197-237

Menzel, E. (1974). A Group of Chimpanzees in a 1-Acre Field: Leadership and Communication. In A. M. Shrier & F. Stollnitz (Eds.) Behaviour of Nonhuman Primates. New York: Academic Press.

McGinn, C. (1982). The Character of Mind. Oxford: Oxford University Press.

Mitchell, R., Thompson, N. & Miles, H. (1997). Anthropomorphism, Anecdotes, and Animals. New York: SUNY Press.

Moser, P. (1983). Rationality without Surprise: Davidson on Rational Belief. Dialectica 37: 221-226.

Nussbaum, M. (2001). Upheavals of Thought: The Intelligence of Emotions. Cambridge: Cambridge University Press.

Panksepp, J. & Burgdorf, J. (2003). “Laughing Rats and the Evolutionary Antecedents of Human Joy? Physiology and Behavior 79:533-547.

Parker, S. T., Mitchell, R. & Boccia, M. (1994). Self-Awareness in Animals and Humans: Developmental Perspectives. Cambridge: Cambridge University Press.

Penn, D. & Povinelli, D. (2007). On the Lack of Evidence that Non-Human Animals Possess Anything Remotely Resembling a ‘Theory of Mind.’ Philosophical Transactions of the Royal Society B 362: 731-744.

Pepperberg, E. (1999). The Alex Studies: Cognitive and Communicative Abilities of Grey Parrots. Cambridge, MA: Harvard University Press.

Povinelli, D & Vonk, J. (2004). We don’t need a microscope to explore the chimpanzee’s mind.Mind and language 19: 1-28. Reprinted in Hurley and Nudds (Eds.) Rational Animals? 2006. Oxford: Oxford University Press.

Premack, D. & Woodruff, G. (1978). Does the Chimpanzee have a Theory of Mind? Behaviorial and Brain Sciences 1: 515-526.

Proust, J. (2009). Metacognitive states in non-human animals: a defense. In R. Lurz (Ed.) The Philosophy of Animal Minds. Cambridge: Cambridge University Press.

Quine, W. V. O. (1995). From Stimulus to Science. Cambridge, Mass.: Harvard University Press.

Radner, D. and Radner, M. (1989). Animal Consciousness. Buffalo, NY: Prometheus Books.

Rey, G. & Tetzlaff, M. (forthcoming). Systematicity in Honeybee Navigation. In Lurz Ed.) Philosophy of Animal Minds. Cambridge: Cambridge University Press.

Roberts, R. (1996). Propositions and Animal Emotion. Philosophy 71:147-156.

Roberts, R. (2009). The Sophistication of Non-Human Emotion. In R. Lurz (Ed.) The Philosophy of Animal Minds. Cambridge: Cambridge University Press.

Rosenthal, D. (1986). Two Concepts of Consciousness. Philosophical Studies 49: 329-359.

Santos, L., Nissen, A., & Ferrugia, J. (2006). Rhesus Monkeys, Macca mulatta, Know What Others Can and Cannot Hear. Animal Behavior 71:1175-1181.

Savage-Rumbaugh, S., Shanker, S. and Taylor, T. (1998). Apes, Language, and the Human Mind. Oxford: Oxford University Press.

Seager, W. (2004). A Cold Look at HOT Theory. In R. Gennaro (Ed.) Higher-Order Theories of Consciousness. Amsterdam: John Benjamins.

Searle, J. (1983). Intentionality. Cambridge: Cambridge University Press.

Searle, J. (1992). The Rediscovery of Mind. Cambridge, Mass.: MIT Press.

Searle, J. (1994). Animal Minds. Midwest Studies in Philosophy 19: 206-219.

Searle. J. (2001). Rationality in Action. Cambridge, Mass.: MIT Press. Shoemaker, S. (1996). Self-Knowledge and “Inner Sense.” Lecture I: The Object Perception Model. In The First-Person Perspective and Other Essays. Cambridge: Cambridge University Press.

Stich, S. (1978). Belief and Subdoxastic States. Philosophy of Science 45: 499-518.

Stich, S. (1979). Do Animals Have Beliefs? Australasian Journal of Philosophy 57: 15- 28.

Stalnaker, R. (1999). Mental Content and Linguistic Form. In Context and Content. Oxford: Oxford University Press.

Smith, J., Shields, W., & Washburn, D. (2003). The Comparative Psychology of Uncertainty Monitoring and Meta-Cognition. Behavioral and Brain Sciences 26, 317-373.

Sober, E. (1998). Morgan’s Canon. In C. Allen and D. Cummins (Eds.) The Evolution of Mind. Oxford: Oxford University Press.

Sober, E. (2001a). Simplicity. In W.H. Newton-Smith (Ed.), Companion to the Philosophy of Science. Oxford: Blackwell Publishing.

Sober, E. (2001b). The Principle of Conservatism in Cognitive Ethology. In D. Walsh (Ed.) Naturalism, Evolution, and Mind. Cambridge: Cambridge University Press.

Sober, E. (2005). Comparative Psychology Meets Evolutionary Biology: Morgan’s Canon and Cladistic Parsimony. In L. Daston & G. Mitman (Eds.) Thinking With Animals: New Perspectives on Anthropomorphism. New York. Columbia University Press.

Sorabji, R. (1993). Animal Minds and Human Morals: The Origins of the Western Debate. Ithaca: Cornell University Press.

Tetzlaff, M. & Rey, G. (2009). Systematicity in Honeybee Navigation. In R. Lurz (Ed.) Philosophy of Animal Minds. Cambridge: Cambridge University Press.

Tschudin , A.J-P.C. (2001). ‘ Mindreading ’ mammals? Attribution of belief tasks with dolphins . Animal Welfare , 10 , 119 – 127 .

Tye, M. (1995). Ten Problems of Consciousness. Cambridge, Mass.: MIT Press.

Tye, M. (1997). The Problem of Simple Minds: Is There Anything it is Like to be a Honey Bee? Philosophical Studies 88: 289-317.

Wilson, M. D. (1995). Animal Ideas. Proceedings and Addresses of the American Philosophical Association 69:7-25.


b. Further Reading

Recent Volumes of New Essays in the Philosophy of Animal Minds

Lurz, R. (2009). The Philosophy of Animal Minds: New Essays on Animal Thought and Consciousness. Cambridge : Cambridge University Press.

Hurley, S. & Nudds, M. (2006). Rational Animals? Oxford: Oxford University Press.

Articles and Books on Contemporary Issues in Philosophy of Mind

Akins, K. A. (1993) A Bat Without Qualities. In M. Davies and G. Humphreys (Eds.) Consciousness. Oxford: Blackwell.

Allen, C. and Hauser, M. (1991). Concept Attribution in Non-Human Animals:Theoretical and Methodological Problems of Ascribing Complex Mental Processes. Philosophy of Science 58: 221-240.

Allen, C. (1995) Intentionality: Natural and Artificial. In H. Roitblat and J.-A.Meyer (Eds.) Comparative Approaches to Cognitive Science. Cambridge, MA: MIT Press.

Allen, C. (1999). Animal Concepts Revisted: The Use of Self-Monitoring as An Empirical Approach. Erkenntnis 51: 33-40.

Allen, C. (2004). Animal Pain. Noûs 38: 617-643.

Allen, C. (2004). Animal Consciousness. Stanford Encyclopedia of Philosophy.

Bennett, J. (1990). How to Read Minds in Behaviour: A Suggestion from a Philosopher. In A. Whiten’s (Ed.) The Emergence of Mindreading. Oxford: Blackwell.

Bennett, J. (1996). How is Cognitive Ethology Possible? In C. Ristau (Ed.) Cognitive Ethology: The Minds of Other Animals. New Jersey: Lawrence Erlbaum Associates.

Bermúdez, J. (2009). Mindreading in the Animal Kingdom? In R. Lurz (Ed.) The Philosophy of Animal Minds. Cambridge: Cambridge University Press.

Bishop, J. (1980). More Thought on Thought and Talk. Mind 89:1-16. Browne, D. (2004) “Do Dolphins Know Their Own Minds?” Biology & Philosophy 19: 633-653.

Carruthers, P. (1989). Brute Experience. The Journal of Philosophy 86: 258-269.

Carruthers, P. (1998). Animal Subjectivity. Psyche 4, .

Cherniak, C. (1986). Minimal Rationality. Cambridge, MA: MIT Press.

Dennett, D. (1983). Intentional Systems in Cognitive Ethology: The “Panglossian Paradigm” Defended. Behavioral and Brain Sciences 6:343-390.

Dennett, D. (1995). Animal Consciousness: What Matters and Why. Social Research 62: 691-711.

DeGrazia, D. (2009). Self-Awareness in Animals. In R. Lurz (Ed.) The Philosophy of Animal Minds. Cambridge: Cambridge University Press.

Dixon, B. (2001). Animal Emotions. Ethics and the Environment 6.2: 22-30.

Dreckmann, F. (1999). Animal Beliefs and Their Contents. Erkenntnis 51:93-111.

Dretske, F. (1999). Machines, Plants and Animals: The Origins of Agency. Erkenntnis 51: 19-31.

Dummett, M. (1993). Language and Communication. In The Seas of Language. Oxford: Clarendon Press.

Dummett, M. (1993). The Origins of Analytic Philosophy. London: Duckworth.

Fodor, J. (1986). Why Paramecia Don’t Have Mental Representations. Midwest Studies in Philosophy 10: 3-23.

Graham, G. (1993). Belief in Animals. In Philosophy of Mind: An Introduction. Oxford: Blackwell.

Griffiths, P. E. (2003). Basic Emotions, Complex Emotions, Machiavellian Emotions. In Philosophy and the Emotions A. Hatzimoysis (Ed.), Cambridge, CUP: 39-67.

Griffiths, P and Scarantino, A. (in press). Emotions in the Wild: The situated perspective on emotion. in P. Robbins and M. Aydede (eds.) Cambridge Handbook of Situated Cognition, Cambridge: Cambridge University Press.

Heil, J. (1982). Speechless Brutes. Philosophy and Phenomenological Research 42: 400-406.

Heil, J. (1992). Talk and Thought. In The Nature of True Minds. Cambridge: Cambridge University Press.

Jamieson, D. and Bekoff, M. (1992) Carruthers on Nonconscious Experience. Analysis 52: 23-28.

Jamieson, D. (1998). Science, Knowledge, and Animals Minds. Proceedings of the Aristotelian Society 98: 79-102.

Jamieson, D. (2009). What Do Animals Think? In R. Lurz (Ed.) The Philosophy of Animal Minds. Cambridge: Cambridge University Press.

Kornblith, H. (1999). Knowledge in Humans and Other Animals. Philosophical Perspectives 13: 327-346.

Marcus, R. B. (1995). The Anti-Naturalism of Some Language Centered Accounts of Belief. Dialectica 49: 113-129.

McAninch, A., Goodrich, G. & Allen, C. (2009). Animal Communication and Neo- Expressivism. In R. Lurz (Ed.) The Philosophy of Animal Minds. Cambridge: Cambridge University Press.

McGinn, C. (1995). Animal Minds, Animal Morality. Journal of Social Research 62: 731-747.

Millikan, R. G. (1997). Varieties of Purposive Behavior. In R. Mitchell, N. Thompson, and H. L. Miles (Eds.) Anthropomorphism, Anecdotes, and Animals. New York: State University of New York Press.

Nagel, T. (1974). What is it Like to be a Bat? Philosophical Review 83: 435-450.

Papineau, D. (2001). The Evolution of Means-End Reasoning. Philosophy 49: 145-178.

Proust, J. (1999). Mind, Space and Objectivity in Non-Human Animals. Erkenntnis 51: 41-58.

Proust, J. (2000). L’animal intentionnel. Terrain 34:23-36.

Proust, J. (2000). Can Non-Human Primates Read Minds? Philosophical Topics 27:203-232.

Putnam, H. (1992). Intentionality and Lower Animals. In Renewing Philosophy. Cambridge, MA: Harvard University Press.

Radner, D. (1993) Direct Action and Animal Communication. Ratio 6: 135-154.

Radner, D. (1994) Heterophenomenology: Learning About the Birds and the Bees. Journal of Phiosophy 91: 389-403.

Radner, D. (1999). Mind and function in animal communication. Erkenntnis 51: 129-144.

Rescorla, M. (2009). Chrysippus’s Dog as a Case Study in Non-Linguistic Cognition. In R. Lurz (Ed.) The Philosophy of Animal Minds. Cambridge: Cambridge University Press.

Ridge, M. (2001). Taking Solipsism Seriously: Nonhuman Animals and Meta-Cognitive Theories of Consciousness. Philosophical Studies 103: 315-340.

Rollin, B. E. (1989) The Unheeded Cry: Animal Consciousness, Animal Pain and Science. Oxford: Oxford University Press.

Rowlands, M. (2002). Do Animals Have Minds? In Animals Like Us. New York: Verso.

Routley, R. (1981). Alleged Problems in Attributing Beliefs and Intentionality to Animals. Inquiry, 24, 385-417.

Saidel, E. (2002). Animal Minds, Human Minds. In M. Bekoff, C. Allen, and G. M. Burghardt The Cognitive Animal. Cambridge, MA: MIT Press.

Saidel, E. (2009). Attributing Mental Representations to Animals. In R. Lurz (Ed.) The Philosophy of Animal Minds. Cambridge: Cambridge University Press.

Smith, P. (1982). On Animal Beliefs. Southern Journal of Philosophy 20, 503-512.

Sober, E. (2001). The Principle of Conservatism in Cognitive Ethology. In Denis M. Walsh (ed.) Naturalism, Evolution, and Mind. Cambridge University Press.

Sober, E. (2001). Comparative Psychology Meets Evolutionary Biology – Morgan’s Canon and Cladistic Parsimony. In L. Daston and G. Mitman (Eds.) Thinking With Animals – New Perspective on Anthropomorphism. Columbia University Press.

Stephan, A. (1999). Are Animals Capable of Concepts? Erkenntnis 51:79-92.

Sterelny, K. (1995). Basic Minds. Philosophical Perspectives 9: 251-270.

Sterelny, K. (2000). Primate Worlds. In C. Heyes and L. Huber (Eds.) Evolution and Cognition. Cambridge, MA: MIT Press.

Stich, S. (1983). Animal Beliefs. In From Folk Psychology to Cognitive Science. Cambridge, MA: MIT Press.

Ward, A. (1988). Davidson on Attributions of Beliefs to Animals. Philosophia 18: 97-106.

Historical Works on Animal Minds

Arnold, D. G. (1995). Hume on the Moral Difference Between Humans and Other Animals. History of Philosophy Quarterly 12: 303-316.

Beauchamp, T. L. (1999). Hume on the Nonhuman Animal. Journal of Medicine and Philosophy 24:322-335.

Boyle, D. (2003). Hume on Animal Reason. Hume Studies 29: 3-28.

Churchill, J. (1989). If a Lion Could Talk. Philosophical Investigations 12: 308-324.

Fuller, B. A. G. (1949). The Messes Animals Make in Metaphysics. The Journal of Philosophy 46: 829—838.

Frongia, G. (1995). Wittgenstein and the Diversity of Animals. Monist 78: 534-552.

Glock, H. J. (2000). Animals, Thoughts and Concepts. Synthese 123:35-64.

Gordon, D. M. (1992). Wittgenstein and Ant-Watching. Biology and Philosophy 7: 13- 25.

Harrison, P. (1992). Descartes on Animals. Philosophical Quarterly 42: 219-227.

Seidler, M. J. (1977). Hume and the Animals. Southern Journal of Philosophy 15:361- 372.

Squadrito, K. (1980). Descartes, Locke and the Soul of Animals. Philosophy Research Archives 6.

Squadrito, K. (1991). Thoughtful Brutes: The Ascription of Mental Predicates to Animals in Locke’s Essay. Dialogos 91: 63-73.

Sorabji, R. (1992). Animal Minds. Southern Journal of Philosophy 31: 1-18.

Tranoy, K. (1959). Hume on Morals, Animals, and Men. Journal of Philosophy 56: 94- 192.

Ancient Greek Skepticism

Although all skeptics in some way cast doubt on our ability to gain knowledge of the world, the term 'skeptic' actually covers a wide range of attitudes and positions. There are skeptical elements in the views of many Greek philosophers, but the term 'ancient skeptic' is generally applied either to a member of Plato's Academy during its skeptical period (c. 273 B.C.E to 1st century B.C.E.) or to a follower of Pyrrho (c. 365 to 270 B.C.E.). Pyrrhonian skepticism flourished from Aenesidemus' revival (1st century B.C.E.) to Sextus Empiricus, who lived sometime in the 2nd or 3rd centuries C.E. Thus the two main varieties of ancient skepticism: Academic and Pyrrhonian.

The term 'skeptic' derives from a Greek noun, skepsis, which means examination, inquiry, consideration. What leads most skeptics to begin to examine and then eventually to be at a loss as to what one should believe, if anything, is the fact of widespread and seemingly endless disagreement regarding issues of fundamental importance. Many of the arguments of the ancient skeptics were developed in response to the positive views of their contemporaries, especially the Stoics and Epicureans, but these arguments have been highly influential for subsequent philosophers and will continue to be of great interest as long as there is widespread disagreement regarding important philosophical issues.

Nearly every variety of ancient skepticism includes a thesis about our epistemic limitations and a thesis about suspending judgment. The two most frequently made objections to skepticism target these theses. The first is that the skeptic's commitment to our epistemic limitations is inconsistent. He cannot consistently claim to know, for example, that knowledge is not possible; neither can he consistently claim that we should suspend judgment regarding all matters insofar as this claim is itself a judgment. Either such claims will refute themselves, since they fall under their own scope, or the skeptic will have to make an apparently arbitrary exemption. The second sort of objection is that the alleged epistemic limitations and/or the suggestion that we should suspend judgment would make life unlivable. For, the business of day-to-day life requires that we make choices and this requires making judgments. Similarly, one might point out that our apparent success in interacting with the world and each other entails that we must know some things. Some responses by ancient skeptics to these objections are considered in the following discussion.
(Hankinson [1995] is a comprehensive and detailed examination of ancient skeptical views. See Schmitt [1972] and Popkin [1979] for discussion of the historical impact of ancient skepticism, beginning with its rediscovery in the 16th Century, and Fogelin [1994] for an assessment of Pyrrhonian skepticism in light of contemporary epistemology. The differences between ancient and modern forms of skepticism has been a controversial topic in recent years-see especially, Annas [1986], [1996], Burnyeat [1984], and Bett [1993].)

1. The Distinction Between Academic and Pyrrhonian Skepticism

The distinction between Academic and Pyrrhonian skepticism continues to be a controversial topic. In the Second Century C.E., the Roman author Aulus Gellius already refers to this as an old question treated by many Greek writers (Attic Nights 11.5.6, see Striker [1981/1996]). The biggest obstacle to correctly making this distinction is that it is misleading to describe Academic and Pyrrhonian skepticism as distinctly unified views in the first place since different Academics and Pyrrhonists seem to have understood their skepticisms in different ways. So even though the terms Academic and Pyrrhonian are appropriate insofar as there are clear lines of transmission and development of skeptical views that unify each, we should not expect to find a simple account of the distinction between the two.


2. Academic Skepticism




a. Arcesilaus

Following Plato's death in 347 B.C.E., his nephew Speusippus became head of the Academy. Next in line were Xenocrates, Polemo and Crates. The efforts of the Academics during this period were largely directed towards developing an orthodox Platonic metaphysics. When Crates died (c. 272 B.C.E.) Arcesilaus of Pitane (c. 318 to 243 B.C.E.) became the sixth head of the Academy. Another member of the Academy, Socratides, who was apparently in line for the position, stepped down in favor of Arcesilaus (DL 4.32); so it seems he was held in high regard by his predecessors, at least at the time of his appointment. (See Long [1986] for discussion of the life of Arcesilaus.)

i. Platonic innovator

According to Diogenes Laertius (=DL), Arcesilaus was "the first to argue on both sides of a question, and the first to meddle with the traditional Platonic system [or: discourse, logos] and by means of question and answer, to make it more of a debating contest" (4.28, translation after R.D. Hicks).

Diogenes is certainly wrong about Arcesilaus being the first to argue on both sides of a question. This was a long standing practice in Greek rhetoric commonly attributed to the Sophists. But Arcesilaus was responsible for turning Plato's Academy to a form of skepticism. This transition was probably supported by an innovative reading of Plato's books, which he possessed and held in high regard (DL 4.31).

Diogenes' remark that Arcesilaus 'meddled' with Plato's system and made it more of a debating contest indicates a critical attitude towards his innovations. Diogenes (or his source) apparently thought that Arcesilaus betrayed the spirit of Platonic philosophy by turning it to skepticism.

Cicero, on the other hand, in an approving tone, reports that Arcesilaus revived the practice of Socrates, which he takes to be the same as Plato's.

"[Socrates] was in the habit of drawing forth the opinions of those with whom he was arguing, in order to state his own view as a response to their answers. This practice was not kept up by his successors; but Arcesilaus revived it and prescribed that those who wanted to listen to him should not ask him questions but state their own opinions. When they had done so, he argued against them. But his listeners, so far as they could, would defend their own opinion" (de Finibus 2.2, translated by Long and Sedley, 68J, see also de Natura Deorum 1.11).

Arcesilaus had (selectively) derived the lesson from Plato's dialogues that nothing can be known with certainty, either by the senses or by the mind (de Oratore 3.67, on the topic of Plato and Socrates as proto-skeptics, see Annas [1992], Shields [1994] and Woodruff [1986]). He even refused to accept this conclusion; thus he did not claim to know that nothing could be known (Academica 45).

ii. Attack on the Stoics

In general, the Stoics were the ideal target for the skeptics; for, their confidence in the areas of metaphysics, ethics and epistemology was supported by an elaborate and sophisticated set of arguments. And, the stronger the justification of some theory, the more impressive is its skeptical refutation. They were also an attractive target due to their prominence in the Hellenistic world. Arcesilaus especially targeted the founder of Stoicism, Zeno, for refutation. Zeno confidently claimed not only that knowledge is possible but that he had a correct account of what knowledge is, and he was willing to teach this to others. The foundation of this account is the notion of katalêpsis: a mental grasping of a sense impression that guarantees the truth of what is grasped. If one assents to the proposition associated with a kataleptic impression, i.e. if one experiences katalepsis, then the associated proposition cannot fail to be true. The Stoic sage, as the perfection and fulfillment of human nature, is the one who assents only to kataleptic impressions and thus is infallible.

Arcesilaus argued against the possibility of there being any sense-impressions which we could not be mistaken about. In doing so, he paved the way for future Academic attacks on Stoicism. To summarize the attack: for any sense-impression S, received by some observer A, of some existing object O, and which is a precise representation of O, we can imagine circumstances in which there is another sense-impression S', which comes either (i) from something other than O, or (ii) from something non-existent, and which is such that S' is indistinguishable from S to A. The first possibility (i) is illustrated by cases of indistinguishable twins, eggs, statues or imprints in wax made by the same ring (Lucullus 84-87). The second possibility (ii) is illustrated by the illusions of dreams and madness (Lucullus 88-91). On the strength of these examples, Arcesilaus apparently concluded that we may, in principle, be deceived about any sense-impression, and consequently that the Stoic account of empirical knowledge fails. For the Stoics were thorough-going empiricists and believed that sense-impressions lie at the foundation of all of our knowledge. So if we could not be certain of ever having grasped any sense-impression, then we cannot be certain of any of the more complex impressions of the world, including what strikes us as valuable. Thus, along with the failure to establish the possibility of katalepsis goes the failure to establish the possibility of Stoic wisdom (see Hankinson [1995], Annas [1990] and Frede [1983/1987] for detailed discussions of this epistemological debate).

iii. On suspending judgment

In response to this lack of knowledge (whether limited to the Stoic variety or knowledge in general), Arcesilaus claimed that we should suspend judgment. By arguing for and against every position that came up in discussion he presented equally weighty reasons on both sides of the issue and made it easier to accept neither side (Academica 45). Diogenes counts the suspension of judgment as another of Arcesilaus' innovations (DL4.28) and refers to this as the reason he never wrote any books (4.32). Sextus Empiricus (Outlines of Pyrrhonism [generally referred to by the initials of the title in Greek, PH] 1.232) and Plutarch (Adversus Colotes 1120C) also attribute the suspension of judgment about everything to him.

Determining precisely what cognitive attitude Arcesilaus intended by "suspending judgment" is difficult, primarily because we only have second and third hand reports of his views (if indeed he endorsed any views, see Dialectical Interpretation below). To suspend judgment seems to mean not to accept a proposition as true, i.e. not to believe it. It follows that if one suspends judgment regarding p, then he should neither believe that p nor should he believe that not-p (for this will commit him to the truth of not-p). But if believing p just means believing that p is true, then suspending judgment regarding everything is the same as not believing anything. If Arcesilaus endorsed this, then he could not consistently believe either that nothing can be known or that one should consequently suspend judgment.

iv. Dialectical Interpretation

One way around this problem is to adopt the dialectical interpretation (advanced by Couissin [1929]). According to this interpretation, Arcesilaus merely showed the Stoics that they didn't have an adequate account of knowledge, not that knowledge in general is impossible. In other words, knowledge will only turn out to be impossible if we define it as the Stoics do. Furthermore, he did not show that everyone should suspend judgment, but rather only those who accept certain Stoic premises. In particular, he argued that if we accept the Stoic view that the Sage never errs, and since katalepsis is not possible, then the Sage (and the rest of us insofar as we emulate the Sage) should never give our assent to anything. Thus the only way to achieve sagehood, i.e. to consistently avoid error, is to suspend judgment regarding everything and never risk being wrong (Lucullus 66-67, 76-78, see also Sextus Empiricus, Against the Logicians [generally referred to by the initial M, for the name of the larger work from which it comes, Adversus Mathematikos] 7.150-57). But the dialectical Arcesilaus himself neither agrees nor disagrees with this.


v. Practical Criterion: to eulogon

The biggest obstacle to the dialectical interpretation is Arcesilaus' practical criterion, to eulogon. Arcesilaus presented this criterion in response to the Stoic objection that if we were to suspend judgment regarding everything, then we would not be able to continue to engage in day to day activities. For, the Stoics thought, any deliberate action presupposes some assent, which is to say that belief is necessary for action. Thus if we eliminate belief we will eliminate action (Plutarch, Adversus Colotes 1122A-F, LS 69A).

Sextus remarks that

"inasmuch as it was necessary . . . to investigate also the conduct of life, which cannot, naturally, be directed without a criterion, upon which happiness-that is, the end of life-depends for its assurance, Arcesilaus asserts that he who suspends judgment about everything will regulate his inclinations and aversion and his actions in general by the rule of 'the reasonable [to eulogon],' and by proceeding in accordance with this criterion he will act rightly; for happiness is attained by means of wisdom, and wisdom consists in right actions, and the right action is that which, when performed, possesses a reasonable justification. He, therefore, who attends to 'the reasonable' will act rightly and be happy" (M 7.158, translated by Bury).

There is a good deal of Stoic technical terminology in this passage, including the term eulogon itself, and this may seem to support the dialectical interpretation. On this view, Arcesilaus is simply showing the Stoics both that their account of knowledge is not necessary for virtue, and that they nonetheless already have a perfectly acceptable epistemic substitute, to eulogon (see Striker [1980/1996]). But this raises the question, why would Arcesilaus make such a gift to his Stoic adversaries? It would be as if, Maconi's words, "Arcesilaus first knocked his opponent to the ground and then gave him a hand up again" (1988: 248). Such generosity would seem to be incompatible with the purely dialectical purpose of refutation. Similarly, if he had been arguing dialectically all along, there seems to be no good reason for him to respond to Stoic objections, for he was not presenting his own views in the first place. On the other hand, the proponent of the dialectical view could maintain that Arcesilaus has not done any favors to the Stoics by giving them the gift of to eulogon; rather, this 'gift' may still be seen as a refutation of the Stoic view that a robust knowledge is necessary for virtue.

An alternative to the dialectical view is to interpret to eulogon as Arcesilaus' own considered opinion regarding how one may live well in the absence of certainty. This view then encounters the earlier difficulty of explaining how it is consistent for Arcesilaus to endorse suspending judgment on all matters while at the same time believing that one may attain wisdom and happiness by adhering to his practical criterion.



b. Carneades

Arcesilaus was succeeded by Lacydes (c. 243 B.C.E.), and then Evander and Hegesinus in turn took over as heads of the Academy. Following Hegesinus, Carneades of Cyrene (c. 213 to 129 B.C.E.), perhaps the most illustrious of the skeptical Academics, took charge. Rather than merely responding to the dogmatic positions that were currently held as Arcesilaus did, Carneades developed a wider array of skeptical arguments against any possible dogmatic position, including some that were not being defended. He also elaborated a more detailed practical criterion, to pithanon. As was the case with Arcesilaus, he left nothing in writing, except for a few letters, which are no longer extant (DL 4.65).

i. Socratic Dialectic

Carneades employed the same dialectical strategies as Arcesilaus (Academica 45, Lucullus 16), and similarly found his inspiration and model in Plato's Socrates. The Socratic practice which Carneades employed, according to Cicero, was to try to conceal his own private opinion, relieve others from deception and in every discussion to look for the most probable solution (Tusculan Disputations 5.11, see also de Natura Deorum 1.11).

In 155 B.C.E., nearly one hundred years after Arcesilaus' death in 243, Carneades is reported to have gone as an Athenian ambassador to Rome. There he presented arguments one day in favor of justice and the next he presented arguments against it. He did this not because he thought that justice should be disparaged but rather to show its defenders that they had no conclusive support for their view (Lactantius, LS 68M). Similarly, we find Carneades arguing against the Stoic conception of the gods, not in order to show that they do not exist, but rather to show that the Stoics had not firmly established anything regarding the divine (de Natura Deorum 3.43-44, see also 1.4). It seems then that Carneades was motivated primarily by the Socratic goal of relieving others of the false pretense to knowledge or wisdom and that he pursued this goal dialectically by arguing both for and against philosophical positions.


ii. On ethical theory

But whereas Arcesilaus seemed to limit his targets to positions actually held by his interlocutors, Carneades generalized his skeptical attack, at least in ethics and epistemology. The main task of Hellenistic ethics was to determine the summum bonum, the goal at which all of our actions must aim if we are to live good, happy lives. Carneades listed all of the defensible candidates, including some that had not actually been defended, in order to argue for and against each one and show that no one in fact knows what the summum bonum is, if indeed there is one (de Finibus 5.16-21). He may have even intended the stronger conclusion that it is not possible to acquire knowledge of the summum bonum, assuming his list was exhaustive of all the serious candidates.


iii. On the Stoic sage

As with Arcesilaus, Carneades also focused much of his skeptical energy on the Stoics, particularly the views of the scholarch Chrysippus (DL 4.62). The Stoics had developed a detailed view of wisdom as life in accordance with nature. The Stoic sage never errs, he never incorrectly values the goods of fortune, he never suffers from pathological emotions, and he always remains tranquil. His happiness is completely inviolable since everything he does and everything he experiences is precisely as it should be; and crucially, he knows this to be true. Even though the Stoics were extremely reluctant to admit that anyone had so far achieved this extraordinary virtue, they nonetheless insisted that it was a real possibility (Luc. 145, Tusc. 2.51, Seneca Ep. 42.1, M 9.133, DL 7.91).

As a dialectician, Carneades carefully examined this conception of the sage. Sometimes he argued, contrary to the Stoic view, that the sage would in fact assent to non-kataleptic impressions and thus that he was liable to error (Luc. 67); for he might form opinions even in the absence of katalepsis (Luc. 78). But he also apparently argued against the view that the sage will hold mere opinions in the absence of katalepsis (Luc. 112). Presumably he didn't himself endorse either position since the issue that had to be decided first was whether katalepsis was even possible. In other words, if certainty is possible, then of course the sage should not settle for mere opinion. But if it is not possible, then perhaps he will be entitled to hold mere opinions, provided they are thoroughly examined and considered.


iv. On epistemology

Just as Carneades generalized his skeptical attack on ethical theories, he also argued against all of his predecessors' epistemological theories (M 7.159). The main task of Hellenistic epistemology was to determine the criterion (standard, measure or test) of truth. If the criterion of truth is taken to be a sort of sense-impression, as in the Stoic theory, then we will not be able to discover any such impression that could not in principle appear true to the most expertly trained and sensitive perceiver and yet still be false (M 7.161-65, see Arcesilaus' 'Attack on the Stoics' above). But if we can discover no criterial sense-impression, then neither will the faculty of reason alone be able to provide us with a criterion, insofar as we accept the empiricist view (common among Hellenistic philosophers) that nothing can be judged by the mind that hasn't first entered by the senses.

We have no evidence to suggest that Carneades also argued against a rationalist, or a priori approach to the criterion.


v. Practical criterion: to pithanon

According to Sextus, after arguing against all the available epistemological theories, Carneades himself needed to advance a criterion for the conduct of life and the attainment of happiness (M 7.166). Sextus does not tell us why it was necessary for Carneades to do so, but it was probably for the same reason that Arcesilaus had presented his practical criterion-namely, in response to the objection that if there were no epistemic grounds on which to prefer one impression over another then, despite all appearances, we cannot rationally govern our choices. Thus, Carneades expounded his practical criterion, to pithanon.

First he noted that every sense impression exists in two distinct relations: one relative to the object from which it comes, the "impressor", and the other relative to the perceiver. The first relation determines what we ordinarily think of as truth: does the impression correspond to its object or not? The second relation determines plausibility: is the impression convincing to the perceiver or not? Rather than relying on the first relation, Carneades adopted the convincing impression [pithanê phantasia] as the criterion of truth, even though there will be occasions on which it fails to accurately represent its object. Yet, he apparently thought that these occasions are rare and so they do not provide a good reason for distrusting the convincing impressions. For such impressions are reliable for the most part, and in actual practice, life is regulated by what holds for the most part (M 7.166-75, LS 69D).

Sextus also reports the refinements Carneades made to his criterion. If we are considering whether we should accept some impression as true, we presumably have already found it to be convincing, but we should also consider how well it coheres with other relevant impressions and then thoroughly examine it further as if we were cross-examining a witness. The amount of examination that a convincing impression requires is a function of its importance to us. In insignificant matters we make use of the merely convincing impression, but in weighty matters, especially those having to do with happiness, we should only rely on the convincing impressions that have been thoroughly explored (M 7.176-84).

Cicero translates Carneades' pithanon with the Latin terms probabile and veri simile, and he claims that this criterion is to be employed both in everyday life and in the Academic dialectical practice of arguing for and against philosophical views (Luc. 32, see also Contr.Ac. 2.26, and Glucker [1995]). The novel feature of this criterion is that it does not guarantee that whatever is in accordance with it is true. But if it is to play the dialectical role explicitly specified by Cicero and suggested by Sextus' report, then it must have some connection with truth. This is especially clear in the case of sense-impressions: the benefit of thoroughly examining sense-impressions is that we may rule out the deceptive ones and accept the accurate ones. And we may make a similar case, as Cicero does, for the dialectical examination of philosophical views. A major difficulty in interpreting Carneades' pithanon in this way is that it requires some explanation for how we are able to identify what resembles the truth (veri simile) without being able to identify the truth itself (Luc. 32-33).


vi. Dialectical skeptic or fallibilist?

Even if the fallibilist interpretation of Carneades' criterion is correct, it remains a further issue whether he actually endorsed his criterion himself, or whether he merely developed it dialectically as a possible view. Indeed, even Carneades' student Clitomachus was unable to determine what, if anything, Carneades endorsed (Luc. 139, see also Striker [1980/1996]). A number of difficulties arise if he did endorse his criterion. First, Carneades argued that there is absolutely no criterion of truth (M 7.159) and that would presumably include to pithanon. Second, Clitomachus claims that Carneades endured a nearly Herculean labor "when he cast assent out of our minds, like a wild and savage beast, that is mere opinion and thoughtlessness" (Luc. 108). Thus it would seem to be inconsistent for him to accept a moderate, fallible form of assent if it leads to holding opinions.

We may more simply deal with Carneades' criterion by noting that sometimes he argued so zealously in support of some view that people reasonably, but incorrectly, assumed that he accepted it himself (Luc. 78, Fin. 5.20). Thus we may say that Carneades only advanced views dialectically but remained uncommitted to any of them. His criterion in this case would be the disappointing consequence of Stoic epistemological commitments-disappointing (as in the case with the dialectical reading of Arcesilaus' eulogon) because the Stoics believed these same commitments led to a much more robust criterion.

On the other hand, Cicero endorses a fallibilist interpretation of to pithanon which he seems to think was also endorsed by Carneades himself. This interpretation was developed by another of Carneades' students, Metrodorus, and by Cicero's teacher, Philo. We also have evidence that Carneades made an important distinction between assent and approval that he may have appealed to in this context (Luc. 104, see Bett [1990]). He limits assent to the mental event of taking a proposition to be true and adopts the term 'approval' for the more modest mental event of taking a proposition to be convincing but without making any commitment to its truth. If this distinction is viable it would allow Carneades to approve of his epistemological criterion without committing himself at any deeper theoretical level. In other words Carneades could appeal to his criterion for his very adoption of that criterion: it is pithanon but not certain that to pithanon is the criterion for determining what we should approve of. Cicero claims that Carneades made just this sort of move in the case of his rejection of the possibility of Stoic katalepsis: it is probabile (= pithanon), but not certain, that katalepsis is not possible (Luc. 110, see Thorsrud [2002]).



c. Philo and Antiochus

According to Sextus Empiricus, most people divide the Academy into three periods: the first, the so-called Old Academy, is Plato's; the second is the Middle Academy of Arcesilaus; and the third is the New Academy of Carneades. But, he remarks, some also add a fourth Academy, that of Philo, and a fifth Academy, Antiochus' (PH 1.220). Philo was head of the Academy from about 110 to 79 B.C.E. His interpretation of Academic skepticism as a mitigated form that permits tentative approval of the view that survives the most dialectical scrutiny is recorded and examined in Cicero's Academica, and in the earlier version of this dialogue, the Lucullus. The Lucullus is just one of the two books that constituted the earlier version. The second book, now lost was called Catulus, after one of the main speakers. Cicero later revised these books, dividing them into four; but only part of the first of those four, what is usually referred to as the Academica posteriora, has survived. Nevertheless, we have enough of these books to get a pretty good sense of the whole work (see Griffin [1997], Mansfeld [1997]).

Philo apparently claimed that some sense-impressions very well may be true but that we nonetheless have no reliable way to determine which ones these are (Luc. 111, see also 34). Similarly, Sextus attributes to Philo the view that "as far the Stoic standard (i.e. apprehensive appearance [= kataleptic impression]) is concerned, objects are inapprehensible, but as far as the nature of the objects themselves is concerned they are apprehensible" (PH 1.235, translated by Annas and Barnes). He may have made these remarks in order to underwrite the Academic practice of accepting certain views as resembling the truth; for there must be some truth in the first place-even if we don't have access to it-in order for something to resemble it.

Under the pressure of Stoic objections to his fallibilist epistemology Philo apparently made some controversial innovations in Academic philosophy. Cicero refers to these innovations but doesn't discuss them in any detail (Luc. 11-12), nor did he accept them himself, preferring Philo's earlier view of the Academy and the dialectical practices of Carneades. Philo's innovation may have been to commit himself to the metaphysical claim that some impressions are indeed true by providing arguments to that effect. So rather than rely on the likelihood that some impressions are true he may have sought to establish this more firmly. He then may have lowered the standard for knowledge by giving up the internalist requirement that one be able to identify which impressions are true and adopted instead the externalist position that just having true impressions, as long as they have the right causal history, is enough for one to have knowledge (see Hankinson [1997] for this interpretation, see also Tarrant [1985] and Brittain [2001]).

After Philo, Antiochus (c. 130 to c. 68 B.C.E.) led the Academy decidedly back to a form of dogmatism. He claimed that the Stoisc and Peripatetics had more accurately understood Plato and thus he sought to revive these views, including primarily Stoic epistemology and ethics, in his Academy (Cicero examines Antiochus' views in de Finibus 5. Glucker [1978] is a groundbreaking study of Antiochus.).



d. Cicero

Cicero was a lifelong student and practitioner of Academic philosophy and his philosophical dialogues are among the richest sources of information about the skeptical Academy. Although he claims to be a mere reporter of other philosophers' views (Att. 12.52.3), he went to some trouble in arranging these views in dialogue form and most importantly in supplying his own words to express them. In some cases he coined the words he needed thereby teaching philosophy to speak Latin. His philosophical coinages-e.g. essentia, qualitas, beatitudo-have left a lasting imprint on Western philosophy.

He is generally not considered to be an original thinker but it is difficult to determine the extent to which this is true since practically none of the books he relied on have survived and so we do not know how much, or whether, he modified the views he presented. Nevertheless, despite questions of originality, his dialogues express a humane and intelligent view of life. Plutarch, in his biography, claims that Cicero often asked his friends to call him a philosopher because he had chosen philosophy as his work, but merely used oratory to achieve his political ends (Life of Cicero 32.6, Colish [1985] is a comprehensive survey of Cicero's philosophical dialogues, so too MacKendrick [1989], and see Powell [1995] for more recent essays on Cicero's philosophy).


3. Pyrrhonian Skepticism

Pyrrho of Elis (c. 360 to c. 270 BCE), the founder of Pyrrhonian skepticism, is a shadowy figure who wrote nothing himself. What little we know of him comes, for the most part, from fragments of his pupil Timon's poems and from Diogenes Laertius' biography (9.61-108) which is based on a book by Antigonus of Carystus, an associate of Timon. There seem to have been no more disciples of Pyrrho after Timon, but much later in the 1st Century B.C.E., Aenesidemus proposed a skeptical view that he claimed to be Pyrrhonian. Later still in the 2nd Century C.E., Sextus Empiricus recorded a battery of skeptical arguments aimed at all contemporary philosophical views. As with Aenesidemus, Sextus claimed Pyrrho as the founder, or at least inspiration, for the skepticism he reports. The content of these skeptical views, the nature of Pyrrho's influence, and the relations between succeeding stages of Pyrrhonism are controversial topics.



a. Pyrrho and Timon

The anecdotal evidence for Pyrrho tends to be sensational. Diogenes reports, for example, that Pyrrho mistrusted his senses to such an extent that he would have fallen off cliffs or been run over by carts and savaged by dogs had his friends not followed close by (9.62). He was allegedly indifferent to certain norms of social behavior, taking animals to market, washing a pig and even cleaning the house himself (9.66). For the most part we find his indifference presented as a positive characteristic. For example, while on a ship in the midst of a terrible storm he was able to maintain a state of tranquility (9.68). Similarly, Timon presents Pyrrho as having reached a godlike state of calm, having escaped servitude to mere opinion (9.64-5, see also the fragments of Timon's prose works, as recorded by Aristocles, LS 2A and 2B). He was also held in such high regard by his native city that he was appointed as high priest and for his sake they made all philosophers exempt from taxation (9.64). We also find a tantalizing report of a journey to India where Pyrrho mingled with, and presumably learned from, certain naked sophists and magi (9.61, the connection with Indian Buddhism is explored by Flintoff [1980]).

Generally, the anecdotal evidence in Diogenes, and elsewhere, is unreliable, or at least highly suspect. Such reports are more likely colorful inventions of later authors attributed to Pyrrho to illustrate, or caricature, some part of his philosophical view. Nevertheless, he is consistently portrayed as being remarkably calm due to his lack of opinion, so we may cautiously accept such accounts.

The most important testimony to the nature of Pyrrho's skepticism comes from Aristocles, a Peripatetic philosopher of the 2nd Century C.E.:

It is supremely necessary to investigate our own capacity for knowledge. For if we are so constituted that we know nothing, there is no need to continue enquiry into other things. Among the ancients too there have been people who made this pronouncement, and Aristotle has argued against them. Pyrrho of Elis was also a powerful spokesman of such a position. He himself has left nothing in writing, but his pupil Timon says that whoever wants to be happy must consider these three questions: first, how are things by nature? Secondly, what attitude should we adopt towards them? Thirdly, what will be the outcome for those who have this attitude? According to Timon, Pyrrho declared that [1] things are equally indifferent, unmeasurable and inarbitrable. For this reason [2] neither our sensations nor our opinions tell us truths or falsehoods. Therefore, for this reason we should not put our trust in them one bit, but we should be unopinionated, uncommitted and unwavering, saying concerning each individual thing that it no more is than is not, or it both is and is not, or it neither is nor is not. [3] The outcome for those who actually adopt this attitude, says Timon, will be first speechlessness, and then freedom from disturbance . . . (Aristocles apud Eusebius, Praeparatio evangelica 14.18.1-5, translated by Long and Sedley, 1F).

Let us consider Pyrrho's questions and answers in order. First, what are things like by nature? This sounds like a straightforward metaphysical question about the way the world is, independent of our perceptions. If so, we should expect Pyrrho's answer, [1] that things are equally indifferent, unmeasurable and inarbitrable, to be a metaphysical statement. But this will lead to difficulties, for how can Pyrrho arrive at the apparently definite proclamation that things are indefinite? I.e. doesn't his metaphysical statement refute itself by implicitly telling us that things are decidedly indeterminate? If we take this view we may defend Pyrrho by allowing his claim to be exempt from its own scope-so we can determine only this much: every property of every thing is indeterminate (see Bett [2000] for this defense). Alternatively, we may allow Pyrrho to embrace the apparent inconsistency and assert that his claim is itself neither true nor false, but is inarbitrable. The former option seems preferable insofar as the latter leaves Pyrrho with no definite assertion whatsoever and it thus becomes unclear how he could draw the inferences he does from [1] to [2].

On the other hand, we may seek to avoid these difficulties by interpreting Pyrrho's first answer as epistemological. After all, the predicates he uses suggest an epistemological claim is being made. And further, Aristocles introduces this passage by noting that we must investigate our capacity for knowledge and he claims that Pyrrho was a spokesman for the view that we know nothing. Bett [2000] argues against the epistemological reading on the grounds that it doesn't make good sense of the passage as it stands. For if we assume the epistemological reading of [1], that we are unable to determine the natures of things, then it would be pointless to infer from that that [2] our senses lie. It would make much more sense to reverse the inference: one might reasonably argue that our senses lie and thus we are unable to determine the natures of things. Some have proposed emending the text from 'for this reason (dia touto)' to 'on account of the fact that (dia to)' to capture this reversal of the inference. But if we read the text as it stands, we may still explain Aristocles' epistemological focus by pointing out that if [1] things are indeterminate, then the epistemological skepticism will be a consequence: things are indeterminable.

Second, in what way ought we to be disposed towards things? Since things are indeterminate (assuming the metaphysical reading) then no assertion will be true, but neither will any assertion be false. So we should not have any opinion about the truth or falsity of any statement (with the exception perhaps of these meta-level skeptical assertions). Instead, we should only say and think that something no more is than is not, or both is and is not, or neither is nor is not, because in fact that's the way things are. So for example, having accepted [1] (and assuming the predicative reading of 'is' in [2]), I will no longer believe that this book is red, but neither will I believe that it is not red. The book is no more red than not-red, or similarly, it is as much red as not-red.

Third, what will be the result for those who are so disposed? The first result is speechlessness (literally, not saying anything)-but this is odd given that we are encouraged to adopt a form of speech in [2]. Perhaps speechlessness follows after initially saying only that things are no more this than that, etc.; then finally, freedom from disturbance follows. Presumably, the recognition that things are no more to be sought after than not sought after is instrumental in producing tranquility, for if nothing is intrinsically good or bad, we have no reason to ever be distressed, or to be exuberantly joyful. But then it seems we would not be able to even choose one thing over another. Pyrrho's tranquility thus begins to look like a kind of paralysis and this is probably what prompted some of the sensational anecdotes.

Diogenes notes, however, that according to Aenesidemus, Pyrrho exercised foresight in his day-to-day activities, and that he lived to be ninety (9.62). So it seems his tranquility did not paralyze him after all. This may be either because Pyrrho (or Timon) was disingenuous about what he was up to intellectually, or more charitably because he followed appearances (9.106) without ever committing himself to the truth or falsity of what appeared. (See 'Sextus on the skeptical life' below for further discussion).



b. Aenesidemus

We know practically nothing about Aenesidemus except that he lived sometime in the 1st Century B.C.E., and that he dedicated one of his written works to a Lucius Tubero, a friend of Cicero's who was also a member of the Academy. This has led most scholars to suppose that Aenesidemus was a member of the Academy, probably during the period of Philo's leadership, and that his revival of Pyrrhonian skepticism was probably a reaction to Philo's tendency towards fallibilism. Although this is plausible, it makes the fact that Cicero never mentions him quite puzzling.


i. Revival of Pyrrhonism

Aenesidemus' Pyrrhonian Discourses (Pyrrhoneia), like the rest of his works, have not survived, but they are summarized by a ninth century Byzantine patriarch, Photius, who is remarkable in his own right. In his Bibliothêkê (= Bib. ), he summarized 280 books, including the Pyrrhoneia, apparently from memory. It is clear from his summary that he thinks very little of Aenesidemus' work. This is due to his view that Aenesidemus' skepticism makes no contribution to Christian dogma and drives from our minds the instinctive tenets of faith (Bib. 170b39-40). Nevertheless, a comparison of his summaries with the original texts that have survived reveal that Photius is a generally reliable source (Wilson [1994]). So despite his assessment of Aenesidemus' skepticism, the consensus is that he provides an accurate summary of the Pyrrhoneia. The proper interpretation of that summary, however, is disputed.

Aenesidemus was a member of Plato's Academy, apparently during the period of Philo's leadership. Growing dissatisfied with what he considered the dogmatism of the Academy, he sought to revitalize skepticism by moving back to a purer form inspired by Pyrrho. His specific complaint against his contemporary Academics was that they confidently affirm some things, even Stoic beliefs, and unambiguously deny other things. In other words, the Academics, in Aenesidemus' view, were insufficiently impressed by our epistemic limitations.

His alternative was to 'determine nothing', not even the claim that he determines nothing. Instead, the Pyrrhonist says that things are no more one way than another. This form of speech is ambiguous (in a positive sense, from Aenesidemus' perspective) since it neither denies nor asserts anything unconditionally. In other words, the Pyrrhonist will only assert that some property belongs to some object relative to some observer or relative to some set of circumstances. Thus, he will conditionally affirm some things but he will absolutely deny that any property belongs to anything in every possible circumstance. This seems to be what Aenesidemus meant by 'determining nothing', for his relativized assertions say nothing definite about the nature of the object in question. Such statements take the form: it is not the case that X is by nature F. This is a simple denial that X is always and invariably F, though of course X may be F in some cases. But such statements are importantly different from those of the form: X is by nature not-F. For these sorts of statements affirm that X is invariably not-F and that there can be no cases of X that exhibit the property F. The only acceptable form of expression for Aenesidemus then seems to be statements that may sometimes be false (See Woddruff [1988] for this interpretation, also Bett 2000).


ii. The Ten Modes

The kinds of conclusion that Aenesidemus countenanced as a Pyrrhonist can more clearly be seen by considering the kinds of arguments he advanced to reach them. He apparently produced a set of skeptical argument forms, or modes, for the purpose of refuting dogmatic claims regarding the natures of things. Sextus Empiricus discusses one such group, the Ten Modes, in some detail (PH 1.35-163, M 7.345, see also Diogenes Laertius' account of the Ten Modes at 9.79-88, and the partial account in Philo of Alexandria, On Drunkenness 169-205, and see Annas and Barnes [1985] for detailed and critical discussion of all ten modes).

The first mode is designed to show that it is not reasonable to suppose that the way the world appears to us humans is more accurate than the incompatible ways it appears to other animals. This will force us to suspend judgment on the question of how these things are by nature, in and of themselves, insofar as we have no rational grounds on which to prefer our appearances and insofar as we are not willing to accept that something can have incompatible properties by nature. If, for example, manure appears repulsive to humans and delightful to dogs, weare unable to say that it really is, in its nature, either repulsive or delightful, or both repulsive and delightful. It is no more delightful than not-delightful, and no more repulsive than not-repulsive, (again, in its nature).

Just as the world appears in incompatible ways to members of different species, so too does it appear incompatibly to members of the same species. Thus, the second mode targets the endless disagreements among dogmatists. But once again, we will find no rational ground to prefer our own view of things, for if an interested party makes himself judge, we should be suspicious of the judgment he reaches, and not accept it.

The third mode continues the line of reasoning developed in the first two. Just as the world appears in incompatible ways to different people, it also appears incompatibly to the different senses of one and the same person. So, for example, painted objects seem to have spatial dimensions that are not revealed to our sense of touch. Similarly, perfume is pleasant to the nose but disgusting to the tongue. Thus, perfume is no more pleasant than not-pleasant.

The fourth mode shows that differences in the emotional or physical state of the perceiver affects his perception of the world. Being in love, calm and warm, one will experience the cold wind that comes in with his beloved quite differently than if he is angry and cold. We are unable to adjudicate between these incompatible experiences of the cold wind because we have no rational grounds on which to prefer our experience in one set of circumstances to our experience in another. One might say that we should give preference to the experiences of those who are healthy, sane and calm as that is our natural state. But in response, we may employ the second mode to challenge the notion of a single, healthy condition that is universally applicable.

The fifth mode shows that differences in location and position of an observed object relative to the observer will greatly affect the way the object appears. Here we find the oar that appears bent in water, the round tower that appears square from a distance, and the pigeon's neck that changes color as the pigeon moves. These features are independent of the observer in a way that the first four modes are not. But similar to the first four, in each case we are left without any rational grounds on which to prefer some particular location or position over another. Why should we suppose, for example, that the pigeon's neck is really green rather than blue? And if we should propose some proof, or theory, in support of it being really blue, we will have to face the skeptic's demand for further justification of that theory, which will set off an infinite regress.

The sixth mode claims that nothing can be experienced in its simple purity but is always experienced as mixed together with other things, either internally in its composition or externally in the medium in which it is perceived. This being the case, we are unable to ever experience the nature of things, and thus are unable to ever say what that nature is.

The seventh mode appeals to the way different effects are produced by altering the quantity and proportions of things. For example, too much wine is debilitating but the right amount is fortifying. Similarly, a pile of sand appears smooth, but individual grains appear rough. Thus, we are led to conclude that wine is no more debilitating than fortifying and sand is no more smooth than rough, in their natures.

The eighth mode, from relativity, is a paradigm for the whole set of modes. It seeks to show, in general, that something appears to have the property F only relative to certain features of the perceiving subject or relative to certain features of the object. And, once again, insofar as we are unable to prefer one set of circumstances to another with respect to the nature of the object, we must suspend judgment about those natures.

The ninth modes points out that the frequency of encountering a thing affects the way that thing appears to us. If we see something that we believe to be rare it will appear more valuable. And when we encounter some beautiful thing for the first time it will seem more beautiful or striking than it appears after we become familiar with it. Thus, we must conclude, for example, that a diamond is no more valuable than worthless.

Finally, the tenth mode, which bears on ethics, appeals to differences in customs and law, and in general, to differences in the ways we evaluate the world. For some, homosexuality is acceptable and good, and to others it is unacceptable and bad. In and of itself, homosexuality is neither good nor bad, but only relative to some way of evaluating the world. And again, since we are unable to prefer one set of values to another, we are led to the conclusion that we must suspend judgment, this time with respect to the intrinsic value of things.

In each of these modes, Aenesidemus seems to be advancing a sort of relativism: we may only say that some object X has property F relative to some observer or set of circumstances, and not absolutely. Thus his skepticism is directed exclusively at a version of Essentialism; in this case, the view that some object has property F in any and every circumstance. A further question is whether Aenesidemus intends his attack on Essentialism to be ontological or epistemological. If it is epistemological, then he is claiming that we simply cannot know what the nature or essence of some thing is, or even whether it has one. This seems most likely to have been Aenesidemus' position since Photius' summary begins with the remark that the overall aim of the Pyrrhoneia is to show that there is no firm basis for cognition. Similarly, the modes seem to be exclusively epistemological insofar as they compel us to suspend judgment; they are clearly designed to force the recognition that no perspective can be rationally preferred to any other with respect to real natures, or essences. By contrast, the ontological view that there are no essences, is not compatible with suspending judgment on the question.


iii. Tranquility

We do not have enough evidence to determine precisely why Aenesidemus found inspiration in Pyrrho. One important point, however, is that they both promote a connection between tranquility and an acceptance of our epistemic limitations (see Bett [2000] for an elaboration of this view). Diogenes Laertius attributes the view to both Anesidemus and the followers of Timon that as a result of suspending judgment, freedom from disturbance (ataraxia) will follow as a shadow (DL 9.107-8). Similarly, Photius reports Aenesidemus' view that those who follow the philosophy of Pyrrho will be happy, whereas by contrast, the dogmatists will wear themselves out in futile and ceaseless theorizing (Bib. 169b12-30, LS 71C). Although there seem to be important differences in what Pyrrho and Aenesidemus understood by our epistemic limitations, they both promoted tranquility as the goal, or at least end product. In general terms the idea is clear enough: the way to a happy, tranquil existence is to live in accordance with how things seem, including especially our evaluative impressions of the world. Rather than trying to uncover some hidden reality, we should accept our limitations, operate in accordance with custom and habit, and not be disturbed by what we cannot know (see Striker [1990/1996]).



c. Sextus Empiricus

We know very little about Sextus Empiricus, aside from the fact that he was a physician. He may have been alive as early as the 2nd Century C.E. or as late as the 3rd Century C.E. We cannot be certain as to where he lived, or where he practiced medicine, or where he taught, if indeed he did teach. In addition to his philosophical books, he also wrote some medical treatises (referred to at M 7.202, 1.61) which are no longer extant.

There are three philosophical works that have survived. Two of these works are grouped together under the general heading, Adversus Mathematikos-which may be translated as Against the Learned, or Against the Professors, i.e. those who profess to know something worth teaching. This grouping is potentially misleading as the first group of six books (chapters, by current standards) are complete and form a self-contained whole. In fact Sextus refers to them with the title Skeptical Treatises. Each of these books target some specific subject in which people profess to be experts, thus: grammar, rhetoric, mathematics, geometry, astrology and music. These are referred to as M 1 through 6, respectively.

There are five additional books in the second set grouped under the heading Adversus Mathematikos: two books containing arguments against the Logicians (M 7, 8), two books against the Physicists (M 9, 10), and one book against the Ethicists (M 11). This set of books is apparently incomplete since the opening of M 7 refers back to a general outline of skepticism that is in none of the extant books of M.

The third work is the Outlines of Pyrrhonism, in three books. The first book provides an outline summary of Pyrrhonian skepticism and would correspond to the missing portion of M. Books 2 and 3 provide arguments against the Logicians, Physicists and Ethicists, corresponding to M 7 through 11. The discussion in PH tends to be much more concise and carefully worded, though there is greater detail and development of many of the same arguments in M. The nature of the relation between these three works is much disputed, especially since the view presented in PH seems to be incompatible with large portions of M (see Bett [1997]).

The following discussion is limited to the views presented in PH.


i. General Account of Skepticism

Sextus begins his overview of Pyrrhonian skepticism by distinguishing three fundamental types of philosopher: dogmatists, who believe they have discovered the truth; Academics (negative dogmatists), who believe the truth cannot be discovered; and skeptics, who continue to investigate, believing neither that anyone has so far discovered the truth nor that it is impossible to do so. Although his characterization of Academics is probably polemical and unfair, the general distinctions he makes are important.

Sextus understands the skeptic, at least nominally as Pyrrho and Aenesidemus do, as one who by suspending judgment determines nothing, and enjoys tranquility as a result. But, as we will see, his conception of suspending judgment is considerably different from his predecessors'.


ii. The path to skepticism

According to Sextus, one does not start out as a skeptic, but rather stumbles on to it. Initially, one becomes troubled by the kinds of disagreements focused on in Aenesidemus' modes and seeks to determine which appearances accurately represent the world and which explanations accurately reveal the causal histories of events. The motivation for figuring things out, Sextus asserts, is to become tranquil, i.e. to remove the disturbance that results from confronting incompatible views of the world. As the proto-skeptic attempts to sort out the evidence and discover the privileged perspectiveor the correct theory, he finds that for each account that purports to establish something true about the world there is another, equally convincing account, that purports to establish an opposed and incompatible view of the same thing. Being faced with this equipollence, he is unable to assent to either of the opposed accounts and thereby suspends judgment. This, of course, is not what he set out to do. But by virtue of his intellectual integrity, he is simply not able to arrive at a conclusion and so he finds himself without any definite view. What he also finds is that the tranquility that he originally thought would come only by arriving at the truth, follows upon his suspended judgment as a shadow follows a body.

Sextus provides a vivid story to illustrate this process. A certain painter, Apelles, was trying to represent foam on the mouth of the horse he was painting. But each time he applied the paint he failed to get the desired effect. Growing frustrated, he flung the sponge, on which he had been wiping off the paint, at the picture, inadvertently producing the effect he had been struggling to achieve (PH 1.28-29). The analogous point in the case of seeking the truth is that the desired tranquility only comes indirectly, not by giving up the pursuit of truth, but rather by giving up the expectation that we must acquire truth to get tranquility. It is a strikingly Zen-like point: one cannot intentionally acquire a peaceful, tranquil state but must let it happen as a result of giving up the struggle. But again, giving up the struggle for the skeptic does not mean giving up the pursuit of truth. The skeptic continues to investigate in order to protect himself against the deceptions and seductions of reason that lead to our holding definite views.

Arriving at definite views is not merely a matter of intellectual dishonesty, Sextus thinks; more importantly, it is the main source of all psychological disturbance. For those who believe that things are good or bad by nature, are perpetually troubled. When they lack what they believe to be good their lives must seem seriously deficient if not outright miserable, and they struggle as much as possible to acquire those things. But when they finally have what they believe to be good, they spend untold effort in maintaining and preserving those things and live in fear of losing them (PH 1.27).

Sextus' diagnosis is not limited to evaluative beliefs, however. This is clear by virtue of the fact that he provides extensive arguments against physical and logical (broadly speaking, scientific and epistemological) theories also. How, then, do such beliefs contribute to the psychological disturbances that Sextus seeks to eliminate? The most plausible reply is that any such belief that we find Sextus arguing against in PH is one that will inevitably contribute to one's evaluations of the world and thus will contribute to the intense strivings that characterize disturbance. An examination of a sample of the logical and physical theses that Sextus' discusses bears this out. Many of these beliefs played foundational roles in the Epicurean or Stoic systems, and thus were employed to establish ethical and evaluative beliefs. Believing that the physical world is composed of invisible atoms, for example, would not, by itself, produce any disturbance since we must draw inferences from this belief in order for it to have any significance for us with respect to choice and avoidance. So it is more appropriate to look past the disturbance that may be produced by individual, isolated beliefs, and consider instead the effect of accepting a system of interrelated, mutually supporting dogmatic claims.


iii. The Modes of Agrippa

As a supplement to the Ten Modes of Aenesidemus (as well as his Eight Modes aimed at causal explanations, see PH 1.180-85, and Hankinson [1998]), Sextus offers a set of Five Modes (PH 1.164-77) and Two Modes (PH 1.178-79) employed by 'more recent skeptics'. We may gather from Diogenes (9.88) that the more recent skeptic referred to is Agrippa. It is important to point out that Sextus merely reports these modes, he does not endorse them at a theoretical level. That is, he does not claim that they possess any sort of logical standing, e.g. that they are guaranteed to reveal a flaw in dogmatic positions, or that they represent some ideal form of reasoning. Instead, we should think of these modes as part of the general account of skepticism, with which the skeptic's practice coheres (PH 1.16-17). In other words, these modes simply describe the way Sextus and his fellow skeptics behave dialectically.

Agrippa's Five Modes relies on the prevalence of dispute and repeats the main theme of Aenesidemus' Modes: we are frequently faced with dissenting opinions regarding the same matter and yet we have no adequate grounds on which to prefer one view over another. Should a dogmatist offer an account of such grounds, the skeptic may then request further justification, thereby setting off an infinite regress. And presumably, we should not be willing to accept an explanation that is never complete, i.e. one that requires further explaining itself. Should the dogmatist try to put a stop to the regress by means of a hypothesis, the skeptic will refuse to accept the claim without proof, perhaps citing alternative, incompatible hypotheses. And finally, the skeptic will refuse to allow the dogmatist to support his explanation by what he is supposed to be explaining, disallowing any circular reasoning. And of course the skeptic may also avail himself of the observation that what is being explained only appears as it does relative to some relevant conditions, and thus, contrary to the dogmatist's presumption, there is no one thing to be explained in the first place (see Barnes [1990]).


iv. Skepticism versus relativism

Sextus employs these skeptical modes towards quite a different goal from Aenesidemus'. Aenesidemus, as we have seen, countenances relativistic assertions of the form, X is no more F than not F. This is to say that although X is not really, in its nature, F, it is still genuinely F in some particular circumstance. And it is acceptable for the Aenesidemean skeptic to believe that this is the case. But for Sextus, the skeptical refrain, 'I determine nothing' excludes relativistic beliefs as well. It is not acceptable for Sextus to believe that X is F, even with relativistic disclaimers. Instead, Sextus would have us refrain from believing even that X is no more F than not-F. Thus, suspension of judgment extends farther for Sextus than it does for Aenesidemus.


v. The skeptical life

So, skepticism is an ability to discover opposed arguments of equal persuasive force, the practice of which leads first to suspension of judgment and afterwards, fortuitously, to tranquility. This makes Sextus' version of Pyrrhonian skepticism dramatically different from other Western philosophical positions, for it is a practice or activity rather than a set of doctrines. Indeed, insofar as the skeptic is supposed to live without belief (adoxastôs), he could not consistently endorse any philosophical doctrine. But how is it possible to live without beliefs?

The short answer is that one may simply follow appearances and withhold judgment as to whether the world really is as it appears. This seems plausible with respect to physical perceptions, but appearances for Sextus include evaluations, and this creates a complication. For how can the skeptic say "this appears good (or bad) to me, but I don't believe that it is really good or bad"? It seems that there is no difference between evaluative appearances and evaluative beliefs.

One possible response to this problem is to say that Sextus only targets sophisticated, philosophical theories about value, or about physics or logic, but allows everyday attitudes and beliefs to stand. On this view, skepticism is a therapy designed to cure the disease of academics and theoreticians. But it seems that Sextus intends his philosophical therapy to be quite widely applicable. The skeptical life, as he presents it, is an achievement and not merely the recovering of a native innocence lost to philosophical speculation. (See Burnyeat and Frede [1997], Brennan [1999] for the debate regarding what the skeptic is supposed to suspend judgment about.)

Any answer to the question about how the skeptic may live without beliefs will depend on what sort of beliefs we think the skeptic avoids. Nevertheless, an elaboration on living in accordance with appearances comes in the form of the fourfold observances. Rather than investigate the best way to live or even what to do in some particular circumstance, Sextus remarks that the skeptic will guide his actions by (1) nature, (2) necessitation by feelings, (3) laws and customs, and (4) kinds of expertise (PH 1.23-24). Nature provides us with the capacity for perception and thought, and we may use these capacities insofar as they don't lead us to dogmatic belief. Similarly, hunger and thirst will drive us towards food and drink without our having to form any explicit beliefs regarding those physical sensations. One need not accept any nutritional theories to adequately and appropriately respond to hunger and thirst. Laws and customs will inform us of the appropriate evaluations of things. We need not actually believe that the gods exist and that they are benevolent to take part in religious ceremonies or even to act in a manner that is (or at least appears) pious. But note that the skeptic will neither believe that the gods exist nor that they do not exist-he is neither a theist nor an atheist, but agnostic in a very robust sense. And finally, the skeptic may practice some trade or profession without accepting any theories regarding his practice. For example, a carpenter need not have any theoretical or geometrical views about doors in order to be skillful at hanging them. Similarly, a doctor need not accept any physiological theories to successfully heal his patients. The further question, recalling the dispute explored in Burnyeat and Frede [1997], is whether the skeptic merely avoids sophisticated, theoretical beliefs in employing these observances, or whether he avoids all beliefs whatsoever.



4. Skepticism and the Examined Life

A unifying feature of the varieties of ancient skepticism is that they are all concerned with promoting, in some manner of speaking, the benefits of recognizing our epistemic limitations. Thus, ancient skeptics nearly always have something to say about how one may live, and indeed live well, in the absence of knowledge.

The fallibilism that developed in Plato's Academy should be seen in this light. Rather than forego the potential benefits of an examination aimed at acquiring better beliefs, the later Academics opted for a less ambitious criterion, one that would give them merely reliable beliefs. Nonetheless, they maintained a thoroughly skeptical attitude towards the possibility of attaining certainty, but without claiming to have conclusively ruled it out.

The more radical skepticism that we find in Sextus' Outlines of Pyrrhonism suggests a move in a different direction. Rather than explain how or why we should trust the skeptical employment of reason, Sextus avoids the problem altogether by, in effect, refusing to answer. Instead, he would suggest that we consider the reasons in support of some particular answer and the reasons opposed in accordance with the skeptical ability so that we may regain tranquility.



5. Greek and Latin texts, commentaries, and translations

General:

Long and Sedley, eds. (1987), The Hellenistic Philosophers, (Cambridge: Cambridge University Press), is a good place to start. These volumes contain selections from the primary sources grouped by topic. See volume 1, sections 68-72 and the following commentaries (pp. 438-488) for readings on Academic and Pyrrhonian skepticism, and sections 1-3 with commentaries (pp. 13-24) for readings on Pyrrho. Volume 2 contains the original Greek and Latin texts corresponding to the translations in volume 1.

Inwood and Gerson, eds. (1988), Hellenistic Philosophy: Introductory Readings, Indianapolis: Hackett), also contains translated selections from the primary sources for Academic and Pyrrhonian skepticism.

Annas and Barnes, eds. (1985), The Modes Of Scepticism, (Cambridge: Cambridge University Press), is a very useful arrangement and translation of the texts that discuss the different varieties of Pyrrhonian argumentation.

For the Greek edition of Photius' summary of Aenesidemus, see R. Henry, ed. (1962), Photius: Bibliothêque, Tome III, (Paris). For a very readable translation, informative introduction and notes, see N.G. Wilson (1994), Photius: The Bibliotheca, (London: Duckworth).

There have been some recently updated and much improved translations and commentaries on Sextus Empiricus.

Annas, J. and J. Barnes (1994), Sextus Empiricus: Outlines of Scepticism, (Cambridge: Cambridge University Press.

Bett, R. (1997), Sextus Empiricus: Against the Ethicists (Adversus Mathematikos XI), (Oxford: Oxford University Press).

Blank, D. (1998), Sextus Empiricus: Against the Grammarians (Adversus Mathematikos I), (Oxford: Oxford University Press).

Greaves, D.D. (1986), Sextus Empiricus: Against the Musicians (Adversus Mathematikos VI), (Lincoln: University of Nebraska Press).

Mates, B. (1996), The Skeptic Way: Sextus Empiricus's Outlines of Pyrrhonism, Translated with Introduction and Commentary, (Oxford: Oxford University Press).

Many of the primary texts can be found in the Loeb series, which contains facing pages of text in the original language and translation. Among the most important are (all published by Harvard University Press):

Bury, R.G. (1933), trans., Sextus Empiricus: Outlines of Pyrrhonism.

____. (1935), trans., Sextus Empiricus: Against the Logicians

____. (1936), trans., Sextus Empiricus: Against the Physicists, Against the Ethicists.

____. (1949), trans., Sextus Empiricus: Against the Professors. Hicks, R.D. (1925), trans., Diogenes Laertius: Lives of Eminent Philosophers, vols. 1 and 2.

Rackham, H. (1933), trans., Cicero: De Natura Deorum, Academica.

____. (1914), trans., Cicero: De Finibus Bonorum et Malorum.




6. Select bibliography of secondary literature

Annas, J., (1996), 'Scepticism, Old and New', in M. Frede and G. Striker, eds., Rationality in Greek Thought, (Oxford: Clarendon).

____. (1993), The Morality of Happiness, (Oxford: Oxford University Press).

____. (1992), 'Plato the Sceptic', in J. Klagge and N. Smith, eds., Oxford Studies in Ancient Philosophy, Supp. Vol., 43-72.

____. (1990), 'Stoic Epistemology', in S. Everson, ed., Epistemology, (Cambridge: Cambridge University Press).

____. (1986), 'Doing Without Objective Values: Ancient and Modern Strategies', in M. Schofield, et. al., eds., Norms of Nature (Cambridge: Cambridge University Press).

Barnes, J. (1990), The Toils of Scepticism, (Cambridge: Cambridge University Press).

Bett, R. (2000), Pyrrho, his antecedents, and his legacy, (Oxford: Oxford University Press).

____. (1990), 'Carneades' Distinction Between Approval and Assent', Monist 73.1: 3-20.

____. (1993), 'Scepticism and Everyday Attitudes in Ancient and Modern Philosophy', Metaphilosophy 24.4: 363-81.

____. (1989), 'Carneades' pithanon: A Reappraisal of its Role and Status', Oxford Studies in Ancient Philosophy 7: 59-94.

Brennan, T. (1999), Ethics and Epistemology in Sextus Empiricus, (New York: Garland).

Brittain, C. (2001), Philo of Larissa, (Oxford: Oxford University Press).

Burnyeat, M. (1984), 'The Sceptic in his Place and Time', in Rorty, Schneewind and Skinner, eds., Philosophy in History, (Cambridge: Cambridge University Press), 225-54, reprinted in Burnyeat and Frede, eds. (1997).

Burnyeat, M. and M. Frede, Eds. (1997), The Original Sceptics: A Controversy, (Indianapolis: Hackett).

Burnyeat, M., Ed. (1983), The Skeptical Tradition, (Berkeley: University of California Press).

Colish, M. (1985), The Stoic Tradition From Antiquity to the Early Middle Ages, vol. 1, (Leiden: Brill).

Couissin, P. (1929), 'Le Stoicisme de la nouvelle Academie', Revue d'historie de la philosophie 3: 241-76, tr. by Jennifer Barnes and M. Burnyeat as 'The Stoicism of the New Academy', in M. Burnyeat, Ed. (1983) 31-63.

Flintoff, E. (1980), 'Pyrrho and India', Phronesis 25: 88-108.

Fogelin, R. (1994), Pyrrhonian Reflections on Knowledge and Justification, (Oxford: Oxford University Press).

Frede, D. (1996) 'How Sceptical Were the Academic Sceptics?', in R.H. Popkin, ed., Scepticism in the History of Philosophy: A Pan-American Dialogue, 1-26, (Dordrecht: Kluwer Academic).

Frede, M. (1987), Essays in Ancient Philosophy, (Minneapolis: University of Minnesota Press).

____. (1983/1987), 'Stoics and Skeptics on Clear and Distinct Impressions' in M. Burnyeat, ed., (1983), reprinted in Frede (1987), 151-78.

Griffin, M. (1997), 'The Composition of the Academica: Motives and Versions' in Inwood and Mansfeld, eds. (1997), 1-35.

Glucker, J. (1995), 'Probabile, Veri Simile, and Related Terms', in J.G.F. Powell, ed., Cicero the Philosopher: Twelve Papers, (Oxford: Oxford University Press).

____. (1978), Antiochus and the Late Academy, (Gottingen: Vandenhoeck und Ruprecht).

Hankinson, R.J. (1998), Cause and Explanation in Ancient Greek Thought, (Oxford: Oxford University Press).

____. (1997), 'Natural Criteria and the Transparency of Judgement: Antiochus, Philo and Galen on Epistemological Justification', in B. Inwood and J. Mansfeld, Eds. (1997), 161-216.

____. (1995), The Sceptics, (London: Routledge).

Inwood, B., and J. Mansfeld, Eds. (1997), Assent and Argument: Studies in Cicero's Academic Books, (Leiden: Brill).

Long, A.A. (1974), Hellenistic Philosophy: Stoics, Epicureans and Sceptics, (Berkeley: University of California Press).

____. (1986), 'Diogenes Laertius' Life of Arcesilaus', Elenchos 7: 432-49.

____. (1988), 'Socrates in Hellenistic Philosophy', Classical Quarterly 38: 150-71.

MacKendrick, P. (1989), The Philosophical Books of Cicero, (New York: St. Martin's Press).

Maconi, H. (1988), 'Nova non philosophandi philosophia: A review of Anna Maria Ioppolo, Opinione e Scienza', Oxford Studies in Ancient Philosophy 6: 231-253.

Mansfeld, J. (1997), 'Philo and Antiochus in the Lost Catulus', Mnemosyne 50.1: 45-74.

Popkin, R. (1979), The History of Scepticism from Erasmus to Spinoza, (Berkeley: University of California Press).

Powell, J.G.F. (1995), Cicero the Philosopher: Twelve Papers, (Oxford: Oxford University Press).

Schmitt, C. (1972), Cicero Scepticus, (The Hague: Nijhoff).

Shields, C. (1994), 'Socrates Among the Sceptics', in P. Vander Waerdt, Ed. (1994), The Socratic Movement, (Ithaca: Cornell University Press).

Sihvola, J., ed. (2000), Ancient Scepticism and the Sceptical Tradition, (Helsinki : Philosophical Society of Finland).

Striker, G. (1996), Essays on Hellenistic Epistemology and Ethics, (Cambridge: Cambridge University Press).

____. (1990/1996), 'Ataraxia: Happiness as Tranquility' Monist 73: 97-110, repr. in Striker (1996), 183-195.

____. (1981/1996), 'Uber den Unterschied zwischen den Pyrrhoneern und den Akademikern', Phronesis 26: 153-71, repr. and transl. by M.M. Lee as 'On the Difference Between the Pyrrhonists and the Academics' in Striker (1996), 135-49.

____. (1980/1996), 'Sceptical Strategies', in M. Schofield, M. Burnyeat, and J. Barnes, Eds. (1980), Doubt and Dogmatism, 54-83, repr. in Striker (1996), 92-115.

Tarrant, H. (1985), Scepticism or Platonism: the Philosophy of the 4th Academy, (Cambridge: Cambridge University Press).

Thorsrud, H. (2002), 'Cicero on His Academic Predecessors: the Fallibilism of Arcesilaus and Carneades', Journal of the History of Philosophy 40: 1-18.

Woodruff , P. (1988), 'Aporetic Pyrrhonism', Oxford Studies in Ancient Philosophy 6: 139-68.

____. (1986), 'The Skeptical Side of Plato's Method', Revue International de Philosophie 156-57: 22-37.