David Johnson: What Does Academic Skepticism Presuppose?

What Does Academic Skepticism Presuppose?


What Does Academic Skepticism Presuppose?
Arcesilaus, Carneades, and the Argument with Stoic Epistemology

David Johnson

Although some have seen the skepticism of Arcesilaus and Carneades, the two foremost representatives of Academic philosophy, as being merely dialectical in nature, there is evidence that both philosophers held views definitive of their skepticism, views which are a direct consequence of a critique of Stoic epistemology and of a defense against the Stoic argument from apraxia. Moreover, both the critique and defense are articulated within the framework provided by Stoic epistemology.  There is a strong case, then, to be made for the claim that Academic skepticism cannot stand alone, that it necessarily requires the terms, concepts and assumptions of Stoicism as an antecedent condition. In making this case I will treat the views of Arcesilaus and Carneades separately, since there are some important differences between them.

                In order to see the way in which Arcesilaus presupposes dogmatic philosophy, we first have to address the question of whether the skepticism of Arcesilaus was merely dialectical, or whether he held definitive skeptical views of his own.[1] If Arcesilaus was a dialectician who limited himself to arguing against the views of others without proposing any of his own, then his skepticism would only presuppose the existence of opponents holding dogmatic views. Although his dialectical method could not subsist on its own, then, there is no reason why it should necessarily require as dialectical fuel the particular form of dogmatism found in Stoic philosophy. If, on the other hand, as I want to maintain, Arcesilaus held the three interrelated views that nothing can be known, that all people ought to suspend judgment, and that one can use the eulogon, or reasonable, as a practical criterion to guide action, then these views would be parasitic on Stoic philosophy in particular. The first two views presuppose Stoic philosophy because they are the consequence of a critique of Stoic epistemology. The third view presupposes Stoicism first, because it seems to have been developed as a response to the Stoic charge of apraxia, and second, because this defense is articulated using the terminology of, and within the framework provided by, Stoic epistemology.  

                The evidence that Arcesilaus was simply a dialectician is thin. According to Numenius

He [Arcesilaus] did not have it in him ever to express one and the same position, nor, for that matter, did he think such a thing worthy of a shrewd man. And that is why he was called “a clever sophist, cutthroat of novices.” […] He would not allow that he or anyone else was in a position to know anything […] but he would say whatever came into his head and then immediately reversing himself he would knock down that view in more ways than he had used to set it up.[2]

But, as R.J. Hankinson notes, Numenius is a hostile source.[3] Moreover, Arcesilaus is described here as holding the view that nothing can be known, something that would be in tension with the interpretation of him as simply an eristic philosopher. And although Diogenes Laertius also presents Arcesilaus as a dialectician, Arcesilaus is described once again as holding a view, in this case the view that one ought to suspend judgmenta claim he repeats elsewhere (DL, 4.32) and one that is echoed by Sextus (Outlines of Pyrrhonism, 1.232). He describes Arcesilaus as

the first to suspend [making] assertions because of the contradictions among arguments. He was also the first to argue both sides of a question and the first to change the doctrine handed down by Plato, that is, to make it more eristic by the use of question and answer…[4]

Cicero, on the other hand, asserts that Arcesilaus was no mere dialectician and that it was necessary for the wise man to hold views:

…Arcesilaus did not fight with Zeno for the sake of quarrelling but really wanted to discover the truth. None of his predecessors ever formally claimed […] that it was possible for a man to hold no opinions, while it was not only possible but even necessary for a wise man to do so. Arcesilaus thought that this view was true, and respectable and worthy of a wise man.[5]

Moreover, he informs us that Arcesilaus held the view that that one should suspend judgment as a consequence of his holding the view that nothing could be known:

So, Arcesilaus denied that there was anything that could be known […] he judged everything to reside in darkness and that nothing could be discerned or understood. For these reasons, one should neither profess nor affirm nor give approval with assent to anything...[6]

                I want to agree with Cicero that Arcesilaus was not an eristic philosopher, but that he held the two positive, interrelated views that one should suspend judgment because nothing can be known. These views are the consequence of Arcesilaus’ critique of Stoic epistemology, an epistemology that rests on an empirical theory of perception. According to this theory, perception takes place when a perceiver’s organs of sense perception come into contact with the object of perception through a presentation, which is an impression that an object makes on the soul  (M 7.228) that is indicative of both itself and the object which produces it (M 7.161). This is an empirical theory of perception that defines perceiving as being affected materially in the soul by the object perceived.

                The Stoic theory of knowledge builds on this model of perception by first making a qualitative distinction between accurate and inaccurate impressions, which they term graspable and non-graspable presentations, respectively. A graspable presentation is a stimulus or impression coming from an existing object outside of the subject that is a reliable representation of the object because it is “stamped and molded in accordance with the existing object”. A non-graspable presentation either does not come from an existing object, or is not clear and distinct (D.L., 7.46, Acad., 1.40). When a graspable presentation has been received and approved by the subject, i.e., assented to, then it has been grasped. A grasped presentation, because is accurate and reliable and leaves out nothing about the object that can be grasped through sensible perception, is the criterion of knowledge, but it not yet knowledge itself. Rather, a grasped presentation lies between knowledge and ignorance; it is one step on the way to knowledge. Zeno illustrated this point with the simile of a hand. A presentation is like an open hand, assent is like a half-closed hand, grasping is like a closed fist, and knowledge is like a hand over a closed fist. Knowledge is a firmly grasped presentation that cannot be shaken or reversed by argument (Acad., 1.41-42).

                Arcesilaus’ response to this theory of knowledge was to claim that there is no such thing as a graspable presentation—and thus, no criterion of knowledge (Acad. 2.77). Since there is no criterion of knowledge, nothing can be known. And if nothing can be known, we must suspend judgment. These conclusions are presented in two separate arguments. The first argument can be found in Cicero, Acad. 2.40:

1) Some presentations are true, some are false
2) False presentations cannot be grasped
3) There is no true presentation such that there cannot be a false one of the same quality
4) No presentation can be grasped if there is no criterion for distinguishing between true and false presentations
5) Therefore, there are no graspable presentations

The entire argument turns on the third premise. The point of this premise is that whatever one might say about the reliability of a graspable presentation—that it compels assent because it has a vivacity or “a distinctive kind of clear statement to make about the objects of presentation” (Acad. 1.41) that is, as Charlotte Stough phrases it, “of such a nature as to have originated necessarily in that object of which it is in fact the exact replica,”[7] there are many presentations that come from non-existing objects that also meet these criteria, such as hallucinations, dreams, illusions, and impressions that are caused by our limited sensory powers rather than by the object itself.[8] The implications of this argument for the Stoic theory of knowledge are made clear in a second argument, found in Sextus, M, 7.156-57:

1) Everything is ungraspable because there is no criterion of knowledge
2) If the wise man assents to anything, he will assent to the ungraspable
3) Assent to the ungraspable is opinion
4) The wise man does not opine, so the wise man will not assent to anything
5) Refusal to give assent is the suspension of judgment
6) Therefore, the wise man suspends judgment

                One might argue at this point that the skeptic has only demonstrated that the Stoic is forced, by his own principles, to conclude that nothing can be known, and hence that he is trapped by his own epistemology into suspending judgment about everything, rather than that nothing can be known in a more global sense, and that everyone ought to suspend judgment. If this were the case, then one might still be able to argue that Arcesilaus was a dialectician who, through a reductio ad absurdum, forced the Stoic philosopher into accepting unpalatable conclusions, conclusions that Arcesilaus himself need not have accepted. However, as Charlotte Stough points out, Academics accept the Stoic account of perception as the soul being affected or altered by impressions made by external objects.[9] Since this theory of perception is, as I noted earlier, the basis for Stoic epistemology, this limits the skeptic to an empirical psychology as the only possible epistemological framework within which to given an account of how a human being comes to know something. Therefore, Arcesilaus’ critique of Stoic epistemology is implicitly a critique of the possibility of knowledge in general, and the conclusions he reaches must have been intended to have a wider application than merely to the philosophy of Stoicism.

                After showing that nothing can be known and that as a result we must suspend judgment, Arcesilaus seems to have been attacked by the Stoics as putting forward views that make it impossible to act, since, on their view, action requires knowledge:

…There must be a principle which wisdom follows when it begins to do something and this principle must be according to nature. For otherwise impulse […] by which we are driven to act and pursue what is presented, cannot be stimulated. But that which stimulates must first be presented [to the agent] and it must be believed; and this cannot happen if what is presented cannot be distinguished from what is false. For how can the mind be moved to an impulse if there is no judgment as to whether what is presented in according to nature or contrary to it? Similarly, if the mind does not realize what is appropriate to it, it will never do anything at all, will never be driven to anything, will never be stimulated. But if it is ever to be moved, what occurs to the agent must be presented as being true.[10]

For those who hold to such a theory of action, the view that we must suspend judgment because nothing can be known was vulnerable to the argument from apraxia:

…Not even those who concerned themselves a great deal with this matter […] were able to shake the doctrine of suspension of judgment on all questions. But at last the Stoics brought against it like a Gorgon’s head the “argument from inaction” and then gave up.[11]

                The Stoic charge that the skeptic is not able to act is additional evidence that Academic skepticism was more than simply dialectical in nature, as it presupposes that the skeptics themselves did indeed hold the view, as I am claiming, that since nothing can be known, one must suspend judgment. Arcesilaus’ response to the Stoic attack was to propose ‘reasonableness’ as a practical criterion for the conduct of life. Those who adhere to the reasonable will be able to act correctly and attain happiness (M 7.158). The skeptics overcame the problem of how one can follow what is reasonable or plausible while still suspending judgment by making a distinction between assent, which would entail that one had ceased suspending judgment, and impulse, which enables a person to act without holding a view about whether a particular presentation is true.  They maintained that a presentation awakens an impulse, which “moves man to act with respect to what is appropriate for him.”[12] An impulse is a movement of the soul caused by a presentation, a process compared to the tipping of a scale. This solution to the problem presupposes Stoic philosophy because it is a response to a Stoic attack; it also presupposes Stoicism insofar as the specific content of that response—i.e., a description of the relationship between the three movements in the soul of presentation, impulse, and assent—relies on the terms and assumptions of Stoic epistemology.

                The case of Carneades is essentially a variation on the way in which Arcesilaus presupposes Stoic philosophy. Carneades, too, was no mere a dialectician; he also held the view that nothing can be known (Acad. 2.59, 78, 148) because “there is no true presentation such that there could not be a false one just like it.”[13] As in the case of Arcesilaus, we can attribute this view to Carneades because (in addition to the textual evidence cited above which indicates that he held this view) he, like everyone, will be forced to hold the view that nothing can be known as the result of a critique of an epistemology assumed to be the only possible account of knowledge, an assumption Carneades must make, since he shares the Stoic theory of perception. As with Arcesilaus, Carneades’ claim that nothing can be known presupposes Stoicism because it results from a critique of Stoic epistemology.

                Since Carneades held that nothing could be known, when “asked for some criterion for the conduct of life and for the attainment of happiness,” he was “virtually compelled to take a position for himself on the topic” (M, 7.166). This looks very much like the old Stoic charge that the skeptic will not be able to act. Although Carneades also responded to this charge by maintaining with Arcesilaus that knowledge is not necessary for action, he differed from Arcesilaus in explaining what exactly was necessary. Whereas Arcesilaus had argued that assent to presentations was not needed to act, because the reasonable or plausible would enable a person who has suspended judgment to live by eliciting the impulse to action, Carneades thinks that we will need to assent to the plausible presentation or pithanon in order for it to guide action. I think it is important to note that pithanon seems likely to be a criterion for action rather than for knowledge, or for both knowledge and action, since Carneades holds that everything is non-apprehensive or ungraspable, so it is not clear how the pithanon could be a criterion of knowledge. For this reason I don’t think that one can say that Carneades was presenting a positive doctrine or theory of knowledge to replace the Stoic theory. Instead, his doctrine of the pithanon should be seen as a direct response to a Stoic attack.

                Carneades relies on the most basic concepts and assumptions of Stoic epistemology in constructing a counter to the Stoic argument from apraxia. He accepts the idea that the truth of a presentation consists in its correspondence with the object. What he rejects is the possibility that one can inspect the object and its presentation in such a way as to determine whether there is a correspondence between the object and the presentation. All that can be known is whether the presentation appears to the subject having the presentation that it is true (M, 7.167-69), such a presentation he calls an apparently true presentation. An apparently true presentation that is not obscure and seems very intensely to be apparently true is called a plausible presentation, or pithanon (M, 7.171-73). Carneades thinks that we only need to suspend judgment about the truth of a presentation, but not about its apparent truth (Numenius in Prep. Ev., bk. xiv, ch. vii-viii, 736d); he maintains that we can give qualified assent to what is plausible. Academic assent to a plausible presentation is weaker than Stoic assent to a graspable presentation, since we can never know if the apparently true presentation is actually true, we cannot give unqualified assent to it—there is always the possibility that we may be wrong.[14] Nevertheless, the plausible presentation justifies our giving qualified assent and so can serve as a criterion for action (Acad., 2.99).

                The strength of our assent or conviction will vary with the plausibility of the presentation,[15] since the plausibility of a presentation can vary in its degree of plausibility. The first way a presentation can vary in it plausibility is in the way that it is given to us, that is, in the extent to which it appears to be a true and adequate representation of the object to the subject. Some plausible presentations, due to the intensity of their apparent truthfulness, strike a person as more plausible than others (M, 7.173). The second way that a presentation can vary in its plausibility is as the result of the application of criteria to determine the degree of plausibility. A presentation becomes more plausible if it is discovered to cohere with other presentations that are given along with it. Sextus observes that just as doctors do not judge someone to be feverish without a combination of symptoms, we can better judge the plausibility of a single presentation by examining the combination of presentations with which it appears, since presentations are never isolated. For example, the presentation of a person will increase in plausibility if that person’s attributes and external circumstances are also found to match or be in harmony with the presentation (M, 7.176-9). A presentation achieves the highest degree of plausibility if it both coheres with other presentations and is subjected to, and passes, thorough scrutiny. A thoroughly tested presentation is one in which a combination of presentations is rigorously scrutinized in terms of the context in which it appears. This includes an examination of factors such as who is judging the presentation and the conditions that might influence the judgment of this person, the medium in which the judgment takes place, and the manner in which the judgment is made (M, 7.182-3). Finally, the extent to which one will attempt to establish assent or conviction will depend on the seriousness of the matter at hand, and on whether circumstances permit one to employ all of the criteria listed above to determine the degree of assent or conviction (M, 7.184-5).

                Carneades’ concept of the pithanon presupposes Stoicism in the same general way that Arcesilaus’ argument for impulse did. The pithanon is also a response to an (implicit) Stoic attack from apraxia, and the content of that response depends on the ideas and language of Stoic epistemology; we saw that Carneades used the structure of a representationalist epistemology in showing that a plausible belief is like knowledge in being a presentation, though it does not actually qualify as knowledge because it is a presentation without the truth content.

                I hope I have shown that Academic skepticism, for all of its nuance and power, depends in crucial ways on the philosophical assumptions, terms, and claims of Stoicism and that it is impossible to imagine a self-standing version of Academic skepticism that did not presuppose the philosophical constructs of Stoicism. An interesting consideration, then, is what, if anything, remains of Academic skepticism if one does not accept the representationalist assumptions of Stoic epistemology—though one doubts that it was possible conceptually or imaginatively for Hellenistic philosophers to even raise this question.



Pennsylvania State University

University Park, Pennsylvania

About the Author

[1] See R. J. Hankinson, The Sceptics, (London: Routledge, 1995), 77 for a fuller discussion of this issue.

[2] Eusebius, Preparatio Evangelica, trans. Brad Inwood and L.P. Gerson in Hellenistic Philosophy (Indianapolis: Hackett, 1997) [henceforth HP] bk. xiv, ch. vi, 730c-d.

[3] Hankinson, 77.

[4] Diogenes Laertius, HP, 4.28.

[5] Cicero, Academica, HP, 2.76-77.

[6] Cicero, Acad., HP, 1.45.

[7] Charlotte Stough, Greek Skepticism. Berkeley: University of California Press, 1969), 39.

[8] Stough, 43-44.

[9] Stough, 41.

[10] Cicero, Acad., HP, 2.24-25.

[11] Plutarch, Against Colotes, HP, 1122a-b.

[12] Plutarch, Against Colotes, 1122c.

[13] Sextus Empiricus, Against the Mathematicians, HP, 7.154.

[14] See Stough, 58.

[15] This is how Stough, 58, puts the matter.