Arcesilaus (315/4–241/40 BCE) was a member and later leader ofPlato’s Academy. He initiated the skeptical phase of the Platonicschool (‘Academic skepticism’) and was an influentialcritic of the Stoics, especially of their epistemology.

The ancient evidence about Arcesilaus’ philosophy is difficultto evaluate and, in some respects, inconsistent. As a result, scholarsinterpret his skepticism in several ways. Some see his philosophicalactivity as entirely negative or destructive of all views. Others takehim to have held positive views, but not on any philosophical topic,including the possibility of knowledge. Some regard him as havingsupposed on the basis of arguments that nothing could be known, whilestill others view him as someone who refused to accept anyphilosophical theory or proposition as rationally warranted, insistingthat further examination is always required.

• 1. Life and work
• 2. Skepticism: method or doctrine
• 3. Criticism of Stoic epistemology
• 4.Inapprehensibility anduniversal suspension of assent
  • 4.1 TheNon-Rational Non-Belief interpretation
  • 4.2 TheRational Non-Belief interpretation
  • 4.3 TheNon-Rational Belief interpretation
• 5. The practical criterion
  • 5.1 TheNon-Rational Non-Belief interpretation
  • 5.2 TheRational Non-Belief interpretation
  • 5.3 TheNon-Rational Belief interpretation
• 6. Priority of method
• 7. Conclusion
• Bibliography
  • Sources
  • Arcesilaus’ life and philosophical activity
  • Arcesilaus’ skeptical position
  • Arcesilaus’ relation to other philosophers
• Academic Tools
• Other Internet Resources
• Related Entries

1. Life and work

After an early education in geometry and astronomy in his nativePitanê (in Aeolis, the northwest Aegean coast of modern Turkey),Arcesilaus escaped to Athens against his guardian’s wishes. There he issaid to have studied rhetoric in association with Theophrastus(Aristotle’s successor) until c. 295–290 BCE, when he abandonedit to study philosophy in Plato’s Academy with Crantor (d. 276/5) andits leaders Polemo (d. 270/69) and Crates (d.268/7). He became the headof the Academy (‘scholarch’) after Crates’ death andled the school for more than 25 years until his own death in 241/40BCE.

Like Socrates, his philosophical model, and Carneades, who carriedforward his skepticism in the 2^nd c. BCE, Arcesilaus did notwrite any philosophical works. His arguments were initially preservedby his students—including Pythodorus, who wrote up some ofthem, and Lakydes, his successor as scholarch—and in the workof his opponents, most notably, the Stoic Chrysippus, whosereformulation of Stoicism was prompted by Arcesilaus’ criticismsof the views of the first generation of Stoics. But Arcesilaus’arguments were later overlaid by Carneadean elaborations and subsumedinto the general Academic and anti-Academic traditions; so it is onlythrough those later traditions that we know about them. Our knowledgeof his work depends on scraps from the biographical tradition(preserved in Diogenes Laertius and Philodemus) and brief generalreports from later skeptical writers—Cicero and SextusEmpiricus and Plutarch—and their opponents—Antiochusand Numenius (preserved in Cicero and Eusebius respectively). But sincethese offer incompatible interpretations of Arcesilaus’philosophical position, reflecting the writers’ distinctive viewsabout later developments in the skeptical Academy, the precise natureof his skepticism remains controversial.

2. Skepticism: method or doctrine

The central question presented by the inconsistent evidence forArcesilaus’ skepticism is how to reconcile his Socratic methodwith the ‘doctrines’ he is reported to have accepted:

1. that nothing can be known (inapprehensibility, or‘akatalêpsia’ in Greek);
2. that one should suspend assent universally and so form no beliefs(universal suspension of assent, or ‘epochêperi pantôn’); and
3. that one who universally suspends assent still has a ‘practicalcriterion’ of action.

Our sources agree that Arcesilaus’ dialectical methodconstituted the core of his philosophical activity (see e.g., DiogenesLaertius 4.28). This method presents two basic difficulties for anyattempt to reconcile it with these doctrines.

First, his method was dialectical, such that rather than arguing infavor of any doctrine or set of doctrines, Arcesilaus restrictedhimself to arguing against the views proposed by his opponents orinterlocutors. At first sight, this method may not look incompatiblewith affirminginapprehensibility anduniversalsuspension of assent if the repeated result of practicing itwas that the views argued against did not stand up to criticism. Suchrepeated failures could suggest that in fact nothing can be known andthat one should form no beliefs at all.

We can see why Arcesilaus’ dialectical method cautions againstaccepting this suggestion by looking at the model he claimed to befollowing: Socrates’ practice in the dialogues of Plato (seeCicero,Academica 1.44–5,De oratore 3.67,De finibus 2.2,On the Nature of the Gods 1.11). InPlato’s Socratic dialogues, at least, Socrates challenges thepretensions of his interlocutors to knowledge by showing, throughpremises they accept, that they are committed to inconsistent beliefs.To achieve this result, it is crucial that the arguments—thepremises, the inferences, and the conclusions—depend entirely onthe beliefs of the interlocutors. If they do, the result of asuccessful Socratic encounter will be that the interlocutor is at aloss: the interlocutors now recognize that they have inconsistentbeliefs, since they have both their initial reasons for the thesis orknowledge-claim they made and their newly-discerned reasons againstit. If they also hold some generally accepted views about knowledge(for example, that one can’t know something about which one holdsinconsistent beliefs), the interlocutors will be rationallyconstrained to aver that they don’t know whether their thesis is trueor false, and hence to suspend assent on the thesis while awaitingfurther investigation and argument. But no such result holds forSocrates. For, although he represents himself as being in the sameaporetic boat—and may in fact be perplexed for exactly the samereasons—his method does not commit him to the premises,inferences or conclusions of the arguments, or even to the regulatingideas about knowledge. His views (if he has any) are not at issue inthe argument.

There is good evidence that Arcesilaus followed the Socratic modelconsistently. It is clear that he went to some lengths not to makepositive affirmations of any sort in his own right in his arguments(see Diogenes Laertius 4.36, PhilodemusIndex Academicorum20.1–4, cf. 18.40–19.9). Our sources also confirm thatArcesilaus took his method to entail that he did not reveal his ownview on the matter in question in any case, if he had one, including,for instance, the view that the claim argued against is false (seee.g., Cicero De oratore 3.67). Further, our mostdetailed sources actually identify the radical change of position inthe Platonic school he introduced—the transition from the OldAcademy to the skeptical Academy—in terms of his adoption ofthis method (see Diogenes Laertius 4.28, PhilodemusIndexAcademicorum 18.7–16 & 21.36–42 and SextusOutlines of Pyrrhonism 1.220–35, esp. 232). And thisexplains his reputation as a ‘dialectician’ (or, morenegatively, as a ‘sophist’ or ‘eristic’ or‘magician’), as well as why the skeptical Academy came tobe defined primarily by its critical stance towards the doctrines ofother schools (and particularly towards the energetic philosophicalprograms of the new movements initiated by Epicurus and Zeno during hislifetime). But if Arcesilaus followed this model consistently byarguing against every philosophical position that came to his noticeand refraining from making any positive arguments or affirmations onany philosophical question, it is hard to see why we should think thathe accepted any doctrines, includinginapprehensibility anduniversal suspension of assent. Thus, the first difficulty isthat Arcesilaus’ method in principle obscures any views he mayhave held.

The second difficulty involved in reconciling Arcesilaus’dialectical method with doctrines [i]–[iii] is morestraightforward: they are conclusions of some of his best knownarguments, but since these are clearly dialectical anti-Stoicarguments, they depend crucially on Stoic premises. In epistemology, heargued that, despite the Stoics’ commitment to readily accessibleknowledge, certain premises accepted by the Stoics entail that nothingis known and that we should suspend assent universally (see below,sect. 3.). Likewise, the theory of action Arcesilaus defended isparasitic on the Stoics’ and relies on their ethical premises(see below, sect. 5). Given his Socratic method, we only have reason toascribe these doctrines to Arcesilaus himself if we have independentevidence that he accepted those premises shared by Stoics. But there isreason to think that Arcesilaus did not accept anything of Stoicepistemology or ethics. The second difficulty, then, is that theevidence does not give a consistent picture of which, if any,conclusions of his dialectical arguments Arcesilaus may have acceptedin his own right.

The first question about Arcesilaus’ skepticism is thuswhether it involved any commitment to doctrines at all. A negativeanswer to this question—based on something like the twodifficulties given above—yields what is called adialectical interpretation of Arcesilaus (adopted by e.g.,Couissin 1929 and Striker 1980; see Castagnoli 2018 on the senses of‘dialectical’). The primary drawback to this interpretationis that it involves the rejection of a central claim about him in allof our major sources except Philodemus: Cicero, Numenius, Sextus,Diogenes and Plutarch ascribe some degree of commitment to at least oneof these doctrines—that ofuniversal suspension ([ii]above). Rejecting this evidence might be justified by the lateness ofthese sources and their associations with later Academic developments;but this seems hard to maintain when we learn that Arcesilaus’contemporary opponents, including Chrysippus, also ascribeduniversal suspension to him (see PlutarchOnStoic Self-Contradictions 1036a with 1037a, andAgainstColotes 1122a). A dialectical interpretation also risks failingas an interpretation: it cannot explain why Arcesilaus arguedas he did, whether because it denies him any commitments or because itclaims they are entirely opaque to us (see Perin 2013).

If we accept that these considerations constrain us to look for apositive answer to the first question, at least as regards therecommendation of suspending assent about everything, the secondquestion is which of the three candidate doctrines—viz., [i]inapprehensibility, [ii]universal suspension, and[iii] a theory of action without assent—was Arcesilauscommitted to. Since, as numerous sources suggest,universalsuspension is the prescriptive claim that one ought not to formany beliefs, then Arcesilaus cannot follow it and at the same timebelieve it, or anything else, to be true. If we do not wish to saddleArcesilaus with a self-defeating skepticism, we are then faced with athird question: what was the nature of Arcesilaus’ commitment tohis doctrines? The answers to these two questions remain open. But thedominant solutions on offer fall roughly into three groups, eachidentifying a different kind of commitment compatible withuniversal suspension, and so a different answer to the thirdquestion. If the sort of commitment prohibited byuniversalsuspension isrational belief, then three weaker kinds ofcommitment seem to have been open to Arcesilaus:

• Non-RationalNon-Belief (‘NRNB’): a commitment top, which neither is a belief thatp nor is based onreasons.
• RationalNon-Belief (‘RNB’): a commitment top, which is not a belief thatp but is based onreasons.
• Non-RationalBelief (‘NRB’): a commitment top,which is a belief thatp but is not based on reasons.

NRNB supposes that the skeptic universally suspends assentas a natural, psychological reaction to equally convincing (orequipollent) and opposing arguments.Universal suspension, onthis view, isnot a prescription justified through theargument that one ought to suspend assent about everything becauseknowledge is impossible. Rather, since the skeptic’s belief-forming faculties areparalyzed in the face of opposing reasons, she acts by impulse,pursuing what appears appropriate (see sect. 5.1). On anNRNBinterpretation Arcesilaus’ commitments to [ii]universalsuspension and [iii] a practical criterion were founded neither onbelief nor on a prior consideration of reasons (see e.g., Ioppolo 1986;2009; 2018).

RNB allows the skeptic to accept doctrines on rationalgrounds, by distinguishing beliefs from other attitudes that can take theplace of beliefs in chains of inference: in particular,belief-like suppositions that function as hypotheses (see Striker 1980,Bett 1990, and Reinhardt 2018). On theRNB view Arcesilausaccepted [i]–[iii] hypothetically (see Schofield 1999, Perin2010, and Thorsrud 2018).

NRB denies the skeptic accepts doctrines on the basis ofany premises that purport to warrant them. On this view, [i]inapprehensibility and [ii]universal suspension werethe residual and rationally unwarranted beliefs Arcesilaus was leftwith as a result of his philosophical activity (see Frede 1979 &1984, Cooper 2004, Brittain 2005 [2008], and Thorsrud 2009).

As we will see in sects. 4–5, these three accounts ofArcesilaus’ skepticism privilege the evidence for his argumentsin competing ways. To understand and evaluate their interpretivestrategies, we first need to examine Arcesilaus’ principalarguments against Stoic epistemology.

3. Criticism of Stoic epistemology

Arcesilaus’ best known arguments, and the only ones thatsurvive in any detail, are his criticisms of Stoic epistemology (SextusAgainst the Logicians [‘M.’]7.150–9, CiceroAcademica 2passim, esp. 2.66–7 & 2.77).

The Stoic theory of knowledge represented a radical shift inepistemology, since it offered an empirically-based route to the kindof wisdom Socrates had sought (see Frede 1999). Its basis was threenovel claims made by Zeno, the founder of the Stoa (see CiceroAcademica 1.40–2). First, Zeno proposed a newpsychological theory: to form a belief of any kind is to give one’sassent to one’s ‘impression’ (or ‘appearance’:‘phantasia’ in Greek) about the matter.Secondly, he claimed that some of our perceptual impressions are‘cognitive’ or self-warranting, so that assenting to themconstitutes a cognition or apprehension(‘katalêpsis’) of their objects.And, thirdly, he argued that we ought to restrict our assent to justcognitive impressions, since it is contrary to reason to form‘opinions’—that is, mere beliefs whether true orfalse—by assenting to inadequately warranted, non-cognitiveimpressions. But, given that there are cognitive impressions, we canattain infallible knowledge or wisdom by restricting our assent tothem, since our thoughts will then be constituted entirely bycognitions derived from perception or from concepts warranted byperceptual cognitions.

The focus of Arcesilaus’ attack on Zeno’s theory was itscenterpiece, the theory of cognitive impressions. Zeno defined acognitive impression as one that comes from what is, is stamped andimpressed exactly in accordance with it, and is such that it could notbe false (SextusM. 7.248, CiceroAcademica 2.77).This means, roughly, that an impression is cognitive if and only if[a] its propositional content is true, [b] it is caused in theappropriate way for correctly representing its object, and [c] itstruth is thus warranted by the inimitable richness and detail of therepresentational character guaranteed by its causal history—suchthat [a] is entailed by [b]. Arcesilaus’ tactic was to grantthat conditions [a] and [b] are often met, as Zeno claimed, but toargue that condition [c] never obtained (M.7.154,Academica 2.77). Although his detailed arguments forthis have not survived, it is fairly clear from later Academic andStoic arguments that he followed two main lines of attack. One linedepended on the existence of indistinguishable—or, at any rate,indiscernibly distinct—objects, such as twins, or pairs of eggs,manufactured items (statues or impressions on wax of the sameletter-seal), and grains of sand (Academica 2.54–8& 2.84–6,M. 7.408–10). Any of these couldbe mistaken for another no matter how good one’s impression of itwas. The second depended on abnormal states of mind, such as dreams,illusions, and fits of madness (Academica 2.47–53 &2.88–90,M. 7.402–8). In either case, Arcesilausargued that, whether the nature of the objects or of our minds is atfault, it is always possible to have a false impression with exactlythe same propositional content and representational character as atrue one that meets condition [b]. But if so, no impression can beself-warranting in virtue of the way in which its content isrepresented. So condition [c] never obtains. Hence, on the Stoic viewof the requirements for cognition, there is no cognition. And ifknowledge is derived entirely from perceptual cognition and conceptswarranted by it, as Zeno supposed, it follows that nothing can beknown. (Intricate Stoic-Academic debates on these issues lasted foranother 150 years; they can best be traced through the arguments ofChrysippus and Carneades, preserved in some detail inCicero’sAcademica and SextusM. 7.)

The argument is standardly summarized as follows:

1. Some impressions are true (a Stoic view).
2. False impressions are non-cognitive (Zeno’s condition [a]).
3. If the content of a true impression is potentiallyindistinguishable or indiscernible from that of a false impression, itis non-cognitive (Zeno’s condition [c]).
4. The content of all true impressions is potentiallyindistinguishable or indiscernible from that of false impressions(Arcesilaus’ counterexamples).
5. So, there are no cognitive impressions. (SeeAcademica2.40 & 2.83.)

And, since for Zeno knowledge itself depends on assent to cognitiveimpressions, this argument leads to the further conclusion that nothingcan be known (inapprehensibility).

Arcesilaus followed up this argument against the cognitiveimpression with a briefer argument against Zeno’s ideal of wisdom:

5. there are no cognitive impressions (as Arcesilaus has argued),&
6. it is irrational to hold ‘opinions’, i.e., to assent tonon-cognitive impressions (as the Stoics held); therefore,
7. it is irrational to assent to any impressions at all. (SeeM. 7.155–7 &Academica 2.66–7.)

That is, Arcesilaus pointed out to the Stoics that if his argument[1]–[5] against the cognitiveimpression is successful, they are also committed to the conclusionthat it is irrational to assent to anything (universalsuspension).

These arguments are presented in two very different ways in our twosources. In Sextus’ account (followed above), they are presentedas explicitly dialectical arguments, relying on clearly marked Stoicviews, and leading to the conclusion that the Stoic sage will have nobeliefs. In the report of Cicero inAcademica 2, however, weare informed that Arcesilaus was in some way committed to premises andconclusions of both arguments: that is, he agreed that condition [c] ofthe Stoic definition of the cognitive impression could never be met,and hence that nothing can be known; and he maintained premises [5] and[6] of the second argument, and hence concluded that assent to anyimpression was irrational (Academica 2.66–7 & 2.77).This historical interpretation of Arcesilaus’ skepticism issupported elsewhere in Cicero’s dialogues, where we find histories ofphilosophy that have Arcesilaus following Socrates and Plato (andPresocratic philosophers such as Democritus, Parmenides and Empedocles)in concluding that nothing can be known by perception or reason, andhence adopting a method of argument that would lead others to refrainfrom all assent (De oratore 3.67 &Academica 1.43–6; see also PlutarchAgainstColotes 1121f).

Cicero’s interpretation inAcademica 2.66–7 &2.77 faces two problems. The first is that the argument against theexistence of cognitive impressions depends on many facets of theepistemological framework of the Stoics. For the conclusion doesn’tfollow unless it is true that there are impressions, that some aretrue, that there are no other routes to cognition, that the Stoicdefinition of cognition gives necessary and sufficient conditions forknowledge, etc. And there is reason to doubt Cicero’s testimony thatArcesilaus subscribed to these Stoic views, since we have some evidencethat he argued against every aspect of Stoic epistemology andpsychology. Plutarch, for instance, mentions an objection to the Stoictheory of the soul’s interaction with the body, which implies thatArcesilaus argued against the fundamental mechanism of impression inZeno’s account (On Common Conceptions 1078c). Another fragmentfrom Plutarch suggests that Arcesilaus argued against Zeno’s causaltheory of perception (Fragment 215a). And Sextus reports thatArcesilaus also objected to Zeno’s conception of belief as assent to animpression, on the ground that assent is a matter of reason or thought,rather than the acceptance of a physiological item, the impression(M. 7.154).

In these cases, as with his argument against the satisfiability ofcondition [c] of the Stoic definition of the cognitive impression, itseems possible to trace a definite strategy behind Arcesilaus’arguments: he argued against Zeno’s empiricist presuppositions bydeploying Platonic objections and theories (see Schofield 1999,Trabattoni 2005, Vezzoli 2016, and von Staden 1978). One mightconclude, as some did in antiquity, that Arcesilaus therefore had ahidden objective of undermining Stoic or Epicurean empiricism in favorof Platonic doctrine (see SextusOutlines of Pyrrhonism1.234). But Arcesilaus’ method implies that he would argueagainst Platonic doctrines as well, if anyone proposed them. So if hedid hold the view that nothing can be known, it seems more plausible tothink that he held it due to the success of his arguments against allconceptions of knowledge, rather than solely as the conclusion of anargument relying on a particular epistemological theory. Cicero’saccount, then, may give only a partial story of the grounds ofArcesilaus’ skeptical views.

The second problem with the interpretation of Arcesilaus’skepticism inAcademica 2.66–7 & 2.77 is that itrisks self-defeat. The problem lies not in knowing that nothing can beknown, since, on one account(Cicero Academica 1.45), Arcesilaus, unlikeSocrates, explicitly disclaimed such second-order knowledge. It liesrather in believing that nothing can be known in conjunction with thebelief that it is irrational to hold opinions in the absence ofknowledge. If the former is true, it is irrational (and so one oughtnot) to believe the premises of the arguments that support bothinapprehensibility anduniversal suspension.

4.Inapprehensibility andUniversal Suspension of Assent

There are two approaches to resolving this second problem, thatacceptinginapprehensibility anduniversal suspensionmay be self-defeating. TheNRNB view takes a negative route,denying that Arcesilaus was committed toinapprehensibilityanduniversal suspension, at least as a prescriptive claimabout the irrationality of assent (see [7] in sect. 3). By contrast,theRNB andNRB views positively ascribeinapprehensibility anduniversal suspension toArcesilaus, but they maintain that his acceptance of them is notexplained in terms of rational belief of the sort which would lead aStoic convinced by Arcesilaus to a self-defeating position (see sect.2).

4.1 TheNon-Rational Non-Belief interpretation

TheNRNB view of Arcesilaus argues that he wasnotcommitted toinapprehensibility anduniversalsuspension, as aprescriptive claim about theirrationality of assent (see [7] in sect. 3). On this view, the twosources for the anti-Stoic arguments still imply that Arcesilaus was‘committed’ touniversal suspension, but this isunderstood as thedescriptive claim that the skeptic does notassent to anything due to the balance of opposing arguments; and he wascommitted to it only in the sense that he acted in accordance with hisunreflective impressions (see sect. 5.1 below). Thus, there is noconflict between the anti-Stoic sources, Sextus and Cicero, and thosethat report that Arcesilaus’universal suspension iscaused by the equipollence of arguments without mentioning hiscriticism of Stoic epistemology (viz., Diogenes Laertius 4.28, CiceroAcademica 1.45, & SextusOutlines of Pyrrhonism1.232).

This interpretation takes Sextus to imply that Arcesilaus’commitment to a descriptive version ofuniversal suspension isprior to his anti-Stoic argument (M. 7.156–7),outlined above in sect. 3 (see e.g., Ioppolo 2002; 2009). In thisargument he holds that the Stoic who concedes the non-existence ofcognitive impressions is forced to conclude that it is rational to‘withhold assent’ (‘asugkatathetein’)about everything (see [10] below). This conclusion is sufficient tooppose the Stoic thesis that some assents are rational. The fullversion of the argument outlined in sect. 3 is:

5. There are no cognitive impressions, as Arcesilaus has argued.

8. The wise person does not hold ‘opinions’, i.e., assentto non-cognitive impressions, as the Stoics held.
9. Therefore, the wise person does not assent to anything.
10. If one does not to assent to anything, one withholds assent(‘asugkatathetein’) about everything.
11. To withhold assent is to suspend judgment(‘epechein’).
12. Therefore, the wise person suspends judgment about everything.

That Arcesilaus used premise [11] to move from withholding assent tothe suspension of judgment (‘epochê’)indicates, on this account, a commitment toepochê thatis independent of Stoic notions like assent and the irrationality ofholding opinions, because it is reached only through the equipollenceof arguments.

TheNRNB view also interprets Cicero as confirming thatArcesilaus was committed to the descriptive version ofuniversalsuspension, even though CiceroAcademica 2.66–7& 77 reports that Arcesilaus was committed to various components ofhis anti-Stoic arguments (see sect. 3): that there are no cognitiveimpressions, that nothing can be known, that it is irrational to holdopinions, and that it is rational to suspend assent. Cicero may beunreliable here, because he is biased by his own, later conception ofradical skepticism, and in his text one may yet find an alternativeview (see Ioppolo 2008): atAcademica 2.32, Cicero’s pro-Stoiccharacter Lucullus refers to skeptical Academics who concede thateverything is uncertain (‘adêla’) withoutpreferring any views; and these Academics appear to be followers ofArcesilaus (cf.Academica 2.16 & 59). Since theseAcademics’ suspension of judgment is based on the notion ofuncertainty, which is not necessarily Stoic, their skeptical views donot depend on an anti-Stoic critique.

However, there are strong reasons not to read Sextus and Cicero asconfirming that Arcesilaus’ commitment to a descriptive versionofuniversal suspension is independent of his anti-Stoicarguments. Even if Arcesilaus developed a notion of suspension(‘epochê’) before his criticisms of theStoa, premise [11] above conceptualizes it in Stoic terms. It is truethat Arcesilaus in SextusM. 7.156–7 goes beyond thepoint sufficient to oppose the Stoic—viz., that the wise persondoes not assent to anything (see [9] above). But he continued theargument because there is a conceptual difference between not assentingand withholding assent (see e.g., Friedman 2013), and becauseepochê refers to the latter. Withholding assentpresupposes a prior examination of evidence and the recognition of anequipollence among the reasons for competing beliefs. (See also Maconi1988 and Bénatouïl 2011.) As for the evidence of Cicero,even if Lucullus thinks Arcesilaus himself belongs to the group ofAcademics who say that everything is non-evident, he also accusesArcesilaus of appealing to the authority of Presocratics to promote hisview ofinapprehensibility, which crucially presupposes Stoicconditions on knowledge (Academica 2.15). So even Lucullusthinks Arcesilaus’ skepticism is related to his anti-Stoicarguments.

There are further problems with theNRNB view, separatefrom the issues of interpretation mentioned above. For one, it narrowlyrestricts the skeptic to a life of unreflective reaction (see sect.5.1), and therefore does not seem compatible with the patterns ofrationality and inquiry that Arcesilaus engaged with. Its narrowrestriction on the scope of skeptical action is also overly dogmatic:were theNRNB view true, it seems implausible Arcesilaus wouldsee the need for a theory of skeptical action, let alone use theStoic model of non-rational animals.

4.2 TheRational Non-Belief interpretation

TheRNB view of Arcesilaus denies that his acceptance ofinapprehensibility anduniversal suspension isexplained in terms ofbelief in the premises and hence in theconclusions of his arguments. Rather, on this account Arcesilausguides his rational activity by something like a supposition orhypothesis—a set of notions deployed variously in Plato’sdialogues, Theophrastus’ dialectic, and geometrical theory (seeSchofield 1999 and Thorsrud 2018; cf. Bénatouïl & ElMurr 2010). Even the Stoics distinguished hypotheticals fromassertions and arguments, such that one can accept hypotheses and whatfollows from them without asserting them (see Barnes 1997). Arcesilauscould have adapted this kind of theory to account for the rationalactivities of the skeptic. Accounts of impression and assent alsoafford a distinction between beliefs and belief-like imaginings suchas suppositions, which may then take the place of beliefs in chains ofinference. This distinction allows for areasoned commitmentthat falls short of assent (see Striker 1980, Bett 1990, andReinhardt 2018). Arcesilaus, on this view, supposes that we ought tolive without realist commitments that fix our view of the world. His supposition may have been based onpremises—some of which he shared with Zeno—as well as on ageneralization from his philosophical experience, after repeatedlyfinding that rational inquiry does not justify assent.

However, this proposal must address several problems. For instance,it seems doubtful that a rational life can be based on hypotheticalswithout a large web of background beliefs (see Frede 1979 and Bett1989). Without them, the skeptic seems unable to decide whichhypotheses to suppose and when to suppose them. And even if such a lifeis possible, it is not clear how it would be practicallydistinguishable from, and so preferable to, a life based wholly onbelief. If the skeptic regards as hypothetical the very same things weordinarily believe, then skepticism seems unmotivated. (See Thorsrud2010 and Perin 2013 for other objections.) Perhaps one could defendthe possibility of a radically skeptical life of this kind by sayingthat, while its development requires starting with beliefs, over timean increasing number of background beliefs may be substituted withhypotheses, and that the benefits of the skeptical life are of asecond-order, affecting the ease with which the skeptic can change theguiding assumptions of her life.

4.3 TheNon-Rational Belief interpretation

TheNRB view instead argues thatuniversalsuspension isn’t opposed to beliefsper se, but only tobeliefs justified through philosophical theory or reasons generally.The Stoics maintain that the mind is essentially rational, so that itsassent is necessarily reason-responsive (see Coope 2016).Arcesilaus’ skepticism, on this view, challenges the rationalistpresupposition that belief is necessarily and explicitly grounded inreason. This doesn’t preclude that Arcesilaus found himself—asa result of the inadequacy of the arguments for any position, and ofthe equally convincing arguments against it—with the beliefthat nothing can be known. Thus,inapprehensibility is neitherthe conclusion of a deductive argument relying on a theory of knowledgeor of our cognitive faculties, nor an inductive inference from priorinvestigations; it is not a theoretical or even rationally warrantedbelief, but just the way things strike him (see Cooper 2004 andThorsrud 2009).

But in the case ofuniversal suspension, it seems that theview that it is irrational to hold unwarranted beliefs isheld—at least in part—on the basis of a theoretical beliefthat knowledge is very important to acquire and that mere belief is tobe avoided. Cicero, for instance, stresses that Arcesilaus agreed withZeno that it is irrational to hold opinions, i.e., inadequatelywarranted assents (premise [6] in sect. 3, above); and Sextus suggeststhat he thought that individual cases of suspendedbelief—presumably in the light of inconclusivearguments—were good (Outlines of Pyrrhonism 1.233). Andthe view that it is irrational to hold mere beliefs (that is,opinions) depends on a further set of epistemological beliefs aboutthe nature of belief and knowledge. If Arcesilaus was not rationallycommitted to any set of assumptions about the nature and requirementsof rationality or about belief and knowledge—which he ought notto be, given that he had argued against the various views on offer,and hence,ex hypothesi, suspended belief about them—itdoesn’t look like he can believe that one ought not to take beliefs tobe justified.

TheNRB view thus takesuniversalsuspension to be a belief that is not rationally warranted, aswell as the views on which it causally depends. That is, Arcesilausbegan inquiry motivated by a pre-theoretical belief, that philosophicalknowledge is important and mere belief inadequate. And his repeated andextensive investigations left him with the realization that even theseregulating assumptions of his philosophical practice have failed to bewarranted and that no beliefs are justified.

On this view, the radical skeptic has beliefs but doesn’t take themto be justified. This proposal raises problems, too (see Burnyeat1983). It seems that a large part of being a rational agent is toexercise some control over one’s beliefs. Since this control takes theform of a responsiveness to reasons, it does not seem possible forrational agents to give up practices of justification. A relatedobjection is to maintain that even having beliefs, which involves theuse of concepts, is necessarily responsive to reasons (see Williams2004). To have a belief, according to this view, requires making aconscious inference about the proper use of concepts, and consciousinferences are made in virtue of reasons. One may respond that theskeptic isn’t precluding herself from a responsiveness to reasons butrather lacks confidence in them, and that such rationalist theories ofagency and belief are stricter even than the Stoics’, againstwhich Arcesilaus argued (see sect. 5 below).

5. The practical criterion

The third doctrine we might ascribe to Arcesilaus on the basis ofhis sources is a so-called practical criterion, i.e., a theory thatmakes action without assent possible (see [iii] in sect. 2). Arcesilaus’ argument for a ‘practicalcriterion’ responds to two Stoic objections of‘inaction’ (apraxia). The first, found inPlutarch, is that action is impossible without assent, since action iscaused by assent to an impression of something suited to the agent’snature, i.e., ‘oikeion’ (AgainstColotes 1122a–d; cf. CiceroAcademica2.37–8). The second objection, reported by Sextus, is that a goodor successful life is impossible without assent, since a good liferequires action based on knowledge of what is good and bad, and henceassent (M. 7.158; cf. CiceroAcademica 2.39).Arcesilaus’ reported replies to these objections are brief, andaccordingly difficult to interpret (see Bett 1989). His counter to thefirst objection is the suggestion that action is possible withoutassent, since even on the Stoic account animal action is triggereddirectly by their impressions of somethingoikeion: theaddition of assent, and so a belief that the object is in factnaturally suited to the agent, is redundant and liable to be acause of error. In response to the second objection, Arcesilaus arguedthat the person who suspends assent universally will successfully guidetheir actions in light of their sense of what is‘reasonable’ (‘eulogon’).

The three doctrinal interpretations of Arcesilaus’ skepticism under consideration take these arguments in Plutarch and Sextus to support, in different ways, their distinct views of his commitment toinapprehensibility and/oruniversal suspension.

5.1 TheNon-Rational Non-Belief interpretation

Proponents of theNRNB view take the argument of Plutarchto give a general theory of action that supports universalsuspension of judgment as a natural reaction to equally balancedarguments. On this theory all actions are merely impulsive, i.e.,caused just by impressions of what appears suitable(‘oikeion’). Since the skeptic doesn’t makejudgments, the only sense in which she is committed to her impressionsis that she acts on them. It is unclear how this is compatible with theevidence of Sextus on ‘the reasonable’, where the skepticconsiders reasonable justifications in deciding what to do. But someadvocates ofNRNB combine the two so that a class of impulsiveactions count as voluntary if, after their performance, one canreasonably justify them as successful (e.g., Ioppolo 1981; 1986; 2000).

Even allowing for this attenuated sense of the voluntary, it isunclear why Arcesilaus would come to accept this impulsivist theory ofaction, if it were true: since—as the theorymaintains—theory doesn’t inform action, it is difficult toexplain theoretical commitments solely in terms of what appears suitedto an agent (see Maconi 1988, Trabattoni 2005, and Vezzoli2016). AnNRNB reading of ‘the reasonable’therefore concedes that Sextus may have elided important details (seeIoppolo 2018).

5.2 TheRational Non-Belief interpretation

TheRNB view opens up a more promising way to read thebrief counter-arguments in Plutarch and Sextus as a positive theory ofArcesilaus. His counter in Plutarch is that action isn’t always causedby occurrent beliefs—we sometimes act through habit, or byinstinct. By itself, this doesn’t go very far, however, since theStoics will have objected that, even if this were possible, thisaccount couldn’t describe the voluntary and responsible actions of arational agent. (The Stoics defined responsible or voluntary action interms of assent, since this was the mechanism through which ourrationality acts on the world.) But one can read the counter-argumentin Sextus as supplementing that response: there is space forrationality and responsibility, on this view, in the production of theimpressions or thoughts motivating us when we act. We can act inaccordance with what strikes us as the reasonable thing to do uponreflection, but still refrain from assent, i.e., refrain from formingthe belief that this is the right thing to do.

There are two problems facing this interpretation of ‘thereasonable’. The first is that it does not look to be supportedby the evidence to which it appeals. Sextus, the source for the notionof ‘the reasonable’ as the criterion, says that Arcesilausand his followers did not define a criterion and that, when theyseemed to, they did so “a counterblast to that of theStoics” (M. 7.150, Bury trans.). (Sextus’ lateraccount of Arcesilaus in another work is also incompatible with hishypothesizing such a theory; seeOutlines of Pyrrhonism1.232–3.) And Cicero and Numenius, our other sources for theview that Arcesilas was committed toinapprehensibilityanduniversal suspension, do not mention his adoption of apractical criterion—in fact, in both authors it is suggestedthat Arcesilaus did not offer a position on how one might live withoutassent, and that Carneades significantly revised the Academic positionin this respect (Academica 2.32; Numenius fr. 27.14–32,cf. Numenius fr. 26.107–11).

The second problem is that even if the context does not explicitlydemand that Arcesilaus’ practical criterion was a dialecticalploy, the argument Arcesilaus used to support it makes the most senseif it is construed dialectically. The argument he gives is somethinglike this (SextusM. 7.158):

13. a good life depends on practical wisdom;
14. practical wisdom consists in a disposition causing right orsuccessful actions;
15. right or successful actions are those that have a reasonabledefense (or justification);
16. the wise person will be guided by what is reasonable;
17. hence, the wise person will go right or be successful.

Two difficulties face this non-dialectical reading. One is thatthere is no other evidence that Arcesilaus was committed to premises[13] through [16], and they are also ones that Arcesilaus may haveargued against, since it is reported that he argued not just againstthe Stoic theory but against all ethical views (PhilodemusIndexAcademicorum 18.40–19.9, Diogenes Laertius 7.171, Numeniusfr. 25.154–61, cf. fr. 25.41–5).

The second, more pressing difficulty is that, although these premisesare adapted to the Arcesilean context in which nothing can be knownand the wise person does not assent to anything, they are manifestlyvariants of the Stoic theory. The Stoics claimed that a good life isthe result of performing ‘appropriateactions’—defined as “those that, once done, have areasonable defense”—from a disposition of wisdom, i.e.,knowledge of what is good, bad and neither. But if nothing can beknown, as Arcesilaus has already argued ([5]–[7] in sect. 3,above), the wisdom of the sage consists in not having anybeliefs. This disposition will still allow the sage to performappropriate actions, however, if, as the Stoics claim, they aredefined by reasonable defenses or justifications. The connectionbetween performing such actions through a wise disposition and successis, Arcesilaus suggests, something that the Stoics can’t deny, becausethey agree that opinion is the cause of error (this is thejustification for premise [6] in sect. 3, above). Hence, the perfectexercise of our rationality—reflection without assent, asArcesilaus has argued—will lead us to find the action that isappropriate to us as rational animals, i.e., the reasonable thing todo, and this guarantees success. Arcesilaus therefore employs theStoic definition of appropriate action to defend acting on views thatare reasonably justified. But, for the Stoics, what is reasonablyjustified is what conforms with the sage’s knowledge of what isgood, bad, and neither. Arcesilaus, it seems, cannot borrow hisopponents’ theory without also accepting the possibility ofknowledge.

5.3 TheNon-Rational Belief interpretation

TheNRB view can instead deny that Arcesilaus waspersonally committed to defending the life ofuniversalsuspension against Stoic counterattack. The Stoics pointed outthat Arcesilaus’ subversive argument for the rationality ofuniversally suspending assent cannot be true, because it makes action,or at least rational and virtuous action, impossible—but theseare plainly possible (cf. CiceroAcademica 2.37–39). Buteven if this objection did not target his own skeptical view,Arcesilaus was bound by his method to counter it. Hence it isunreasonable to think that he was invested in rationalizing the life ofthe skeptic with a theory of action (see Stopper 1983; for adifferent view of the polemic, see, e.g., Ioppolo 1986, Maconi 1988,and Thorsrud 2009).

6. Priority of Method

Section 2 noted that the central question for the interpretation ofArcesilaus’ skepticism is how to reconcile his method with hisskeptical commitments, and sections 4–5 set out three accounts ofhow his commitments are compatible with his method. A further questionrelates to the purpose of Arcesilaus’ philosophical activity.Competing histories of Arcesilaus’ intentions in Cicero’sAcademica offer different answers (see Allen 2018): at onepoint Cicero suggests that Arcesilaus adopted a Socratic methodafter he acceptedinapprehensibility anduniversal suspension, in order to facilitate suspension ofassent (Academica 1.44–45; cf. SextusOutlines ofPyrrhonism 1.232); but elsewhere he says that Arcesilaus’aim in questioning Zeno was to discover the truth (Academica2.76; cf. CiceroOn the Nature of the Gods 1.11). Soin question is whether Arcesilaus’ method wasin the service of inquiry—independently of his commitments toinapprehensibility oruniversal suspension—ora revival of a Socratic methodology that only reflected skepticalconclusions he already reached.

An argument in favor of the latter is as follows (see Görler1994): if Arcesilaus indeed shared the views that knowledge isimpossible and that holding opinions is irrational—as both theRNB andNRB interpretations say—then he couldnot have genuinely been in the business of inquiry, which aims atknowledge of the truth; hence the only motivation for dialecticalargument Arcesilaus might be left with is the promotion ofuniversal suspension. But this argument ignores the contextfrom which Arcesilaus’ skeptical views emerged and the effectsthey could reasonably be expected to have had on his philosophicalpractice.

On theRNB view, the Academic skeptic, at the start of herphilosophical career, inherits a rational method of inquiry, as well asguiding views about belief and knowledge. But her inheritance is so faruntested (at least by her). As she goes about putting it to work, shemight at first believe that her method and its norms help her to get atthe truth. But she then finds that by arguing in accordance with thosenorms she is wildly successful at combatting any and all positions. Shetherefore comes to suppose on rational grounds—which mayinclude particular arguments against Stoic cognition, the inadequacy ofall non-skeptical theories of knowledge, and her experiences inargument generally—that the norms cannot successfully guide herto truths. But she doesn’t quit her life of inquiry because herskeptical view of the inadequacy of her method depends on that verymethod; it makes little sense for her to act on a view that rejects itsown grounds. Instead she continues to inquire, now treating herinherited norms and guiding views about belief and knowledge only ashypotheses rather than as given. On theRNB view, therefore,Arcesilaus’ skepticism was self-defeating only insofar as itcould not justify abandoning reason.

A similar story can be told with theNRB view. The skepticlooks for the truth, on the assumption that obtaining it is of crucialimportance for her life. But since she consistently fails to find it,it begins to strike her that perhaps she never will. Perhaps, it wasnot, after all, so important for her life to have it: maybe merebelief is all we need. But it doesn’t follow that she should give up(as false) her belief that it is irrational to hold opinions, since itwould only be correct to give it up if it actually is true that merebelief is all she needs—but this is something that her argumentsdon’t warrant, any more than they warrant the oppositeconclusion. AnNRB view, then, suggests thatArcesilaus’ beliefs in the importance of knowledge and theinadequacy of opinion were explicitly non-rational, in the sense thathe was not persuaded that they were warranted by a rational argumentor theory, or even by the extensive arguments he devoted his lifeto. He believed that he hadn’t found knowledge and that it isirrational to assent to anything without knowledge, but realized, as aresult of the unrestricted application of his Socratic method, thatthere were strong reasons against these beliefs. He was thus not in aposition to give his rational assent to the belief that it isirrational to hold opinions—he just found that that was howthings striked him, i.e., that’s what he believed. The Academicskeptic, on this view, is someone whose sustained but pre-theoreticalcommitment to rational investigation undermines her confidence inrationality. The result is not a negative theory—e.g., thetheory that we can’t acquire knowledge owing to the limitations of ourcognitive or rational capacities—but a pervasive lack of theorysustained by a dialectical method.

If either of these stories is correct, we don’t need to denyArcesilaus seached for the truth, and the basic philosophical puzzleabout his radical skepticism is not whether it is possible to livewithout rational beliefs, but whether it is possible to be committed torationality and yet sufficiently detached from it to recognise that,whatever it is, it may not work.

7. Conclusion

It is clear that any interpretation of Arcesilaus must take intoaccount both his reputation as a master dialectician who deployedSocrates’ method ruthlessly against his philosophicalcontemporaries, and his notorious advocacy ofinapprehensibility anduniversal suspension. Giventhe contradictory nature and scarcity of the evidence, it is perhapsnot surprising that modern critics do not agree about the success ofthe ‘dialectical’ or various ‘doctrinal’interpretations of Arcesilaus or about the consistency of the verydifferent kinds of skepticism the latter propose. But further progressis not ruled out, since it is open to us to offer more sophisticatedphilosophical elaborations of those forms of skepticism and to testtheir historical plausibility by appealing to the diverse, but betterattested traditions in the later Academy.

Bibliography

Sources

Collections of Arcesilaus’ sources

• Inwood, Brad and Lloyd Gerson (eds.), 1997,HellenisticPhilosophy: Introductory Readings, second edition, Indianapolis,IN: Hackett.

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• Mette, Hans Joachim, 1984, “Zwei Akademiker heute: Krantorvon Soloi und Arkesilaos von Pitane,”Lustrum 26:7–94.

  [The evidence on Arcesilaus in Greek and Latin, with Germantranslations.]

• Long, A. A. and D. N. Sedley (eds.), 1987,The HellenisticPhilosophers, vol. 1, Cambridge: Cambridge UniversityPress.

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• Vezzoli, Simone, 2016,Arcesilao di Pitane: l’originedel Platonismo neoaccademico, Turnhout: Brepols, pp.149–268.

  [The evidence on Arcesilaus in Greek and Latin, with Italiantranslations.]

Primary Sources

• Cicero,On Academic Scepticism, Charles Brittain(trans.), Indianapolis, IN: Hackett, 2006.

  [English translation ofAcademica.]

• –––,On the Ideal Orator, James May andJakob Wisse (trans.), Oxford and New York: Oxford University Press,2001.

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• –––,On the Nature of the Gods,Academica (Loeb Classical Library 268/Cicero XIX), H. Rackham(trans.), Cambridge, MA: Harvard University Press, 1933.

  [Loeb edition with English translation.]

• –––,De finibus bonorum et malorum (LoebClassical Library 40/Cicero XVII), H. Rackham (trans.), Cambridge, MA:Harvard University Press, 1914.

  [Loeb edition with English translation.]

• –––,De Oratore Book III, inOn theOrator: Book 3.On Fate.Stoic Paradoxes.Divisions of Oratory (Loeb Classical Library 349/Cicero IV),H. Rackham (trans.), Cambridge, MA: Harvard University Press,1942.

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• –––,On Moral Ends, Raphael Woolf(trans.), Cambridge: Cambridge University Press, 2002.doi:10.1017/CBO9780511803659

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• Diogenes Laertius,Lives of the Eminent Philosophers,Tiziano Dorandi (ed.), Cambridge: Cambridge University Press, 2013.doi:10.1017/CBO9780511843440

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• –––,Lives of Eminent Philosophers I& II (Loeb Classical Library 184/5), R. Hicks (trans.), Cambridge,MA: Harvard University Press, 1925.

  [Loeb edition with English translation.]

• –––,Lives of the Eminent Philosophers,Pamela Mensch (trans.), Oxford and New York: Oxford University Press,2018.

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• Numenius,Platonist Philosophy 80 BC to AD 250: An Introductionand Collection of Sources in Translation, George Boys-Stones (ed.),Cambridge: Cambridge University Press, 2018, pp. 40–45.

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• –––,Fragments, E. Des Places (ed.),Paris: Belles Lettres, 1973.

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• –––, 1903,Eusebii PamphiliEvangelicae Praeparationis LibriXV, 4 vols., E. H.Gifford (ed.), Oxford: Oxford University Press, 1903.

  [Greek text with English translation of Eusebius; book 14.4–9contains Numenius’ fragments.]

• Philodemus,Storia dei filosofi [.]Platone el’Academia, Tiziano Dorandi (ed.), Naples: Bibliopolis, 1991.

  [Greek text with Italian translation of Philodemus’IndexAcademicorum.]

• –––, “Philodemus’History of thePhilosophers: Plato and the Academy (PHerc. 1021 and 164),”Paul Kalligas and Voula Tsouna (trans.), in Paul Kalligas, Chloe Balla, EffieBaziotopoulou-Valavani, and Vassilis Karasmanis (eds.),Plato’s Academy: Its Workings and Its History,Cambridge: Cambridge University Press, 2020, pp. 276–383.

  [Greek text, adapted from Dorandi’s edition, with Englishtranslation of Philodemus’Index Academicorum.]

• Plutarch,MoraliaXIIIPart 2: StoicEssays (Loeb Classical Library 470), HaroldCherniss (trans.), Cambridge, MA: Harvard University Press,1976.

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• –––,Moralia XIV (Loeb Classical Library428), Benedict Einarson and Phillip De Lacy (eds.), Cambridge, MA:Harvard University Press, 1967.

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• –––,Moralia XV: Fragments (LoebClassical Library 429), F. H. Sandbach (trans.), Cambridge,MA: Harvard University Press, 1969.

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• Sextus Empiricus,Outlines of Scepticism, Julia Annas andJonathan Barnes (trans.), New York: Cambridge University Press, 1994,second edition 2000.

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• –––, [M]Against the Logicians[Adversus Mathematicos 7–8], Richard Bett (trans.),Cambridge: Cambridge University Press, 2005.
• –––,Outlines of Pyrrhonism (LoebClassical Library 273/Sextus Empiricus I), R. G. Bury (trans.),Cambridge, MA: Harvard University Press, 1933.

  [Loeb edition with English translation.]

• –––,Against Logicians (Loeb ClassicalLibrary 291/Sextus Empiricus II), R. G. Bury (trans.), Cambridge, MA:Harvard University Press, 1935.

  [Loeb edition with English translation.]

Arcesilaus’ life and philosophical activity

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Arcesilaus’ skeptical position

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Arcesilaus’ relation to other philosophers

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