## 1. Life and work




After an early education in geometry and astronomy in his native
Pitane (in Aeolis, the northwest Aegean coast of modern Turkey),
Arcesilaus escaped to Athens against his guardian's wishes. There he is
said to have studied rhetoric in association with Theophrastus
(Aristotle's successor) until c. 295-290 BCE, when he abandoned
it to study philosophy in Plato's Academy with Crantor (d. 276/5) and
its leaders Polemo (d. 270/69) and Crates (d.268/7). He became the head
of the Academy ('scholarch') after Crates' death and
led the school for more than 25 years until his own death in 241/40
BCE.




Like Socrates, his philosophical model, and Carneades, who carried
forward his skepticism in the 2nd c. BCE, Arcesilaus did not
write any philosophical works. His arguments were initially preserved
by his students--including Pythodorus, who wrote up some of
them, and Lakydes, his successor as scholarch--and in the work
of his opponents, most notably, the Stoic Chrysippus, whose
reformulation of Stoicism was prompted by Arcesilaus' criticisms
of the views of the first generation of Stoics. But Arcesilaus'
arguments were later overlaid by Carneadean elaborations and subsumed
into the general Academic and anti-Academic traditions; so it is only
through those later traditions that we know about them. Our knowledge
of his work depends on scraps from the biographical tradition
(preserved in Diogenes Laertius and Philodemus) and brief general
reports from later skeptical writers--Cicero and Sextus
Empiricus and Plutarch--and their opponents--Antiochus
and Numenius (preserved in Cicero and Eusebius respectively). But since
these offer incompatible interpretations of Arcesilaus'
philosophical position, reflecting the writers' distinctive views
about later developments in the skeptical Academy, the precise nature
of his skepticism remains controversial.


## 2. Skepticism: method or doctrine




The central question presented by the inconsistent evidence for
Arcesilaus' skepticism is how to reconcile his Socratic method
with the 'doctrines' he is reported to have accepted:


1. that nothing can be known (*inapprehensibility*, or
'*akatalepsia*' in Greek);
2. that one should suspend assent universally and so form no beliefs
(*universal suspension of assent*, or '*epoche
peri panton*'); and
3. that one who universally suspends assent still has a 'practical
criterion' of action.




Our sources agree that Arcesilaus' dialectical method
constituted the core of his philosophical activity (see e.g., Diogenes
Laertius 4.28). This method presents two basic difficulties for any
attempt to reconcile it with these doctrines.




First, his method was dialectical, such that rather than arguing in
favor of any doctrine or set of doctrines, Arcesilaus restricted
himself to arguing against the views proposed by his opponents or
interlocutors. At first sight, this method may not look incompatible
with affirming *inapprehensibility* and *universal
suspension of assent* if the repeated result of practicing it
was that the views argued against did not stand up to criticism. Such
repeated failures could suggest that in fact nothing can be known and
that one should form no beliefs at all.




We can see why Arcesilaus' dialectical method cautions against
accepting this suggestion by looking at the model he claimed to be
following: Socrates' practice in the dialogues of Plato (see
Cicero, *Academica* 1.44-5, *De oratore* 3.67,
*De finibus* 2.2, *On the Nature of the Gods* 1.11). In
Plato's Socratic dialogues, at least, Socrates challenges the
pretensions of his interlocutors to knowledge by showing, through
premises they accept, that they are committed to inconsistent beliefs.
To achieve this result, it is crucial that the arguments--the
premises, the inferences, and the conclusions--depend entirely on
the beliefs of the interlocutors. If they do, the result of a
successful Socratic encounter will be that the interlocutor is at a
loss: the interlocutors now recognize that they have inconsistent
beliefs, since they have both their initial reasons for the thesis or
knowledge-claim they made and their newly-discerned reasons against
it. If they also hold some generally accepted views about knowledge
(for example, that one can't know something about which one holds
inconsistent beliefs), the interlocutors will be rationally
constrained to aver that they don't know whether their thesis is true
or false, and hence to suspend assent on the thesis while awaiting
further investigation and argument. But no such result holds for
Socrates. For, although he represents himself as being in the same
aporetic boat--and may in fact be perplexed for exactly the same
reasons--his method does not commit him to the premises,
inferences or conclusions of the arguments, or even to the regulating
ideas about knowledge. His views (if he has any) are not at issue in
the argument.




There is good evidence that Arcesilaus followed the Socratic model
consistently. It is clear that he went to some lengths not to make
positive affirmations of any sort in his own right in his arguments
(see Diogenes Laertius 4.36, Philodemus *Index Academicorum*
20.1-4, cf. 18.40-19.9). Our sources also confirm that
Arcesilaus took his method to entail that he did not reveal his own
view on the matter in question in any case, if he had one, including,
for instance, the view that the claim argued against is false (see
e.g., Cicero *De oratore* 3.67). Further, our most
detailed sources actually identify the radical change of position in
the Platonic school he introduced--the transition from the Old
Academy to the skeptical Academy--in terms of his adoption of
this method (see Diogenes Laertius 4.28, Philodemus *Index
Academicorum* 18.7-16 & 21.36-42 and Sextus
*Outlines of Pyrrhonism* 1.220-35, esp. 232). And this
explains his reputation as a 'dialectician' (or, more
negatively, as a 'sophist' or 'eristic' or
'magician'), as well as why the skeptical Academy came to
be defined primarily by its critical stance towards the doctrines of
other schools (and particularly towards the energetic philosophical
programs of the new movements initiated by Epicurus and Zeno during his
lifetime). But if Arcesilaus followed this model consistently by
arguing against every philosophical position that came to his notice
and refraining from making any positive arguments or affirmations on
any philosophical question, it is hard to see why we should think that
he accepted any doctrines, including *inapprehensibility* and
*universal suspension of assent*. Thus, the first difficulty is
that Arcesilaus' method in principle obscures any views he may
have held.




The second difficulty involved in reconciling Arcesilaus'
dialectical method with doctrines [i]-[iii] is more
straightforward: they are conclusions of some of his best known
arguments, but since these are clearly dialectical anti-Stoic
arguments, they depend crucially on Stoic premises. In epistemology, he
argued that, despite the Stoics' commitment to readily accessible
knowledge, certain premises accepted by the Stoics entail that nothing
is known and that we should suspend assent universally (see below,
sect. 3.). Likewise, the theory of action Arcesilaus defended is
parasitic on the Stoics' and relies on their ethical premises
(see below, sect. 5). Given his Socratic method, we only have reason to
ascribe these doctrines to Arcesilaus himself if we have independent
evidence that he accepted those premises shared by Stoics. But there is
reason to think that Arcesilaus did not accept anything of Stoic
epistemology or ethics. The second difficulty, then, is that the
evidence does not give a consistent picture of which, if any,
conclusions of his dialectical arguments Arcesilaus may have accepted
in his own right.




The first question about Arcesilaus' skepticism is thus
whether it involved any commitment to doctrines at all. A negative
answer to this question--based on something like the two
difficulties given above--yields what is called a
*dialectical* 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 interpretation
is that it involves the rejection of a central claim about him in all
of our major sources except Philodemus: Cicero, Numenius, Sextus,
Diogenes and Plutarch ascribe some degree of commitment to at least one
of these doctrines--that of *universal suspension* ([ii]
above). Rejecting this evidence might be justified by the lateness of
these sources and their associations with later Academic developments;
but this seems hard to maintain when we learn that Arcesilaus'
contemporary opponents, including Chrysippus, also ascribed
*universal suspension* to him (see Plutarch *On*
*Stoic Self-Contradictions* 1036a with 1037a, and *Against
Colotes* 1122a). A dialectical interpretation also risks failing
*as an interpretation*: it cannot explain why Arcesilaus argued
as he did, whether because it denies him any commitments or because it
claims they are entirely opaque to us (see Perin 2013).




If we accept that these considerations constrain us to look for a
positive answer to the first question, at least as regards the
recommendation of suspending assent about everything, the second
question is which of the three candidate doctrines--viz., [i]
*inapprehensibility*, [ii] *universal suspension*, and
[iii] a theory of action without assent--was Arcesilaus
committed to. Since, as numerous sources suggest, *universal
suspension* is the prescriptive claim that one ought not to form
any beliefs, then Arcesilaus cannot follow it and at the same time
believe it, or anything else, to be true. If we do not wish to saddle
Arcesilaus with a self-defeating skepticism, we are then faced with a
third question: what was the nature of Arcesilaus' commitment to
his doctrines? The answers to these two questions remain open. But the
dominant solutions on offer fall roughly into three groups, each
identifying a different kind of commitment compatible with
*universal suspension*, and so a different answer to the third
question. If the sort of commitment prohibited by *universal
suspension* is *rational belief*, then three weaker kinds of
commitment seem to have been open to Arcesilaus:


* *Non-Rational
Non-Belief* ('*NRNB*'): a commitment to
*p*, which neither is a belief that *p* nor is based on
reasons.
* *Rational
Non-Belief* ('*RNB*'): a commitment to
*p*, which is not a belief that *p* but is based on
reasons.
* *Non-Rational
Belief* ('*NRB*'): a commitment to *p*,
which is a belief that *p* but is not based on reasons.



*NRNB* supposes that the skeptic universally suspends assent
as a natural, psychological reaction to equally convincing (or
equipollent) and opposing arguments. *Universal suspension*, on
this view, is *not* a prescription justified through the
argument that one ought to suspend assent about everything because
knowledge is impossible. Rather, since the skeptic's belief-forming faculties are
paralyzed in the face of opposing reasons, she acts by impulse,
pursuing what appears appropriate (see sect. 5.1). On an *NRNB*
interpretation Arcesilaus' commitments to [ii] *universal
suspension* and [iii] a practical criterion were founded neither on
belief nor on a prior consideration of reasons (see e.g., Ioppolo 1986;
2009; 2018).



*RNB* allows the skeptic to accept doctrines on rational
grounds, by distinguishing beliefs from other attitudes that can take the
place of beliefs in chains of inference: in particular,
belief-like suppositions that function as hypotheses (see Striker 1980,
Bett 1990, and Reinhardt 2018). On the *RNB* view Arcesilaus
accepted [i]-[iii] hypothetically (see Schofield 1999, Perin
2010, and Thorsrud 2018).



*NRB* denies the skeptic accepts doctrines on the basis of
any premises that purport to warrant them. On this view, [i]
*inapprehensibility* and [ii] *universal suspension* were
the residual and rationally unwarranted beliefs Arcesilaus was left
with 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 of
Arcesilaus' skepticism privilege the evidence for his arguments
in competing ways. To understand and evaluate their interpretive
strategies, we first need to examine Arcesilaus' principal
arguments against Stoic epistemology.


## 3. Criticism of Stoic epistemology




Arcesilaus' best known arguments, and the only ones that
survive in any detail, are his criticisms of Stoic epistemology (Sextus
*Against the Logicians* ['*M.*']
7.150-9**,** Cicero *Academica* 2
*passim*, esp. 2.66-7 & 2.77).




The Stoic theory of knowledge represented a radical shift in
epistemology, since it offered an empirically-based route to the kind
of wisdom Socrates had sought (see Frede 1999). Its basis was three
novel claims made by Zeno, the founder of the Stoa (see Cicero
*Academica* 1.40-2). First, Zeno proposed a new
psychological theory: to form a belief of any kind is to give one's
assent 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 them
constitutes a cognition or apprehension
('*katalepsis**'*) of their objects.
And, thirdly, he argued that we ought to restrict our assent to just
cognitive impressions, since it is contrary to reason to form
'opinions'--that is, mere beliefs whether true or
false--by assenting to inadequately warranted, non-cognitive
impressions. But, given that there are cognitive impressions, we can
attain infallible knowledge or wisdom by restricting our assent to
them, since our thoughts will then be constituted entirely by
cognitions derived from perception or from concepts warranted by
perceptual cognitions.




The focus of Arcesilaus' attack on Zeno's theory was its
centerpiece, the theory of cognitive impressions. Zeno defined a
cognitive impression as one that comes from what is, is stamped and
impressed exactly in accordance with it, and is such that it could not
be false (Sextus *M*. 7.248, Cicero *Academica* 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 the
appropriate way for correctly representing its object, and [c] its
truth is thus warranted by the inimitable richness and detail of the
representational character guaranteed by its causal history--such
that [a] is entailed by [b]. Arcesilaus' tactic was to grant
that conditions [a] and [b] are often met, as Zeno claimed, but to
argue that condition [c] never obtained (*M*.
7.154, *Academica* 2.77). Although his detailed arguments for
this have not survived, it is fairly clear from later Academic and
Stoic arguments that he followed two main lines of attack. One line
depended 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 same
letter-seal), and grains of sand (*Academica* 2.54-8
& 2.84-6, *M*. 7.408-10). Any of these could
be mistaken for another no matter how good one's impression of it
was. 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, Arcesilaus
argued that, whether the nature of the objects or of our minds is at
fault, it is always possible to have a false impression with exactly
the same propositional content and representational character as a
true one that meets condition [b]. But if so, no impression can be
self-warranting in virtue of the way in which its content is
represented. So condition [c] never obtains. Hence, on the Stoic view
of the requirements for cognition, there is no cognition. And if
knowledge is derived entirely from perceptual cognition and concepts
warranted by it, as Zeno supposed, it follows that nothing can be
known. (Intricate Stoic-Academic debates on these issues lasted for
another 150 years; they can best be traced through the arguments of
Chrysippus and Carneades, preserved in some detail in
Cicero's *Academica* and Sextus *M.* 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 potentially
indistinguishable or indiscernible from that of a false impression, it
is non-cognitive (Zeno's condition [c]).
4. The content of all true impressions is potentially
indistinguishable or indiscernible from that of false impressions
(Arcesilaus' counterexamples).
5. So, there are no cognitive impressions. (See *Academica*
2.40 & 2.83.)




And, since for Zeno knowledge itself depends on assent to cognitive
impressions, this argument leads to the further conclusion that nothing
can be known (*inapprehensibility*).




Arcesilaus followed up this argument against the cognitive
impression 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 to
non-cognitive impressions (as the Stoics held); therefore,
7. it is irrational to assent to any impressions at all. (See
*M*. 7.155-7 & *Academica* 2.66-7.)




That is, Arcesilaus pointed out to the Stoics that if his argument
[1]-[5] against the cognitive
impression is successful, they are also committed to the conclusion
that it is irrational to assent to anything (*universal
suspension*).




These arguments are presented in two very different ways in our two
sources. In Sextus' account (followed above), they are presented
as explicitly dialectical arguments, relying on clearly marked Stoic
views, and leading to the conclusion that the Stoic sage will have no
beliefs. In the report of Cicero in *Academica* 2, however, we
are informed that Arcesilaus was in some way committed to premises and
conclusions of both arguments: that is, he agreed that condition [c] of
the 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 any
impression was irrational (*Academica* 2.66-7 & 2.77).
This historical interpretation of Arcesilaus' skepticism is
supported elsewhere in Cicero's dialogues, where we find histories of
philosophy that have Arcesilaus following Socrates and Plato (and
Presocratic philosophers such as Democritus, Parmenides and Empedocles)
in concluding that nothing can be known by perception or reason, and
hence adopting a method of argument that would lead others to refrain
from all assent (*De oratore* 3.67 &
*Academica* 1.43-6; see also Plutarch *Against
Colotes* 1121f).




Cicero's interpretation in *Academica* 2.66-7 &
2.77 faces two problems. The first is that the argument against the
existence of cognitive impressions depends on many facets of the
epistemological framework of the Stoics. For the conclusion doesn't
follow unless it is true that there are impressions, that some are
true, that there are no other routes to cognition, that the Stoic
definition of cognition gives necessary and sufficient conditions for
knowledge, etc. And there is reason to doubt Cicero's testimony that
Arcesilaus subscribed to these Stoic views, since we have some evidence
that he argued against every aspect of Stoic epistemology and
psychology. Plutarch, for instance, mentions an objection to the Stoic
theory of the soul's interaction with the body, which implies that
Arcesilaus argued against the fundamental mechanism of impression in
Zeno's account (*On Common Conceptions* 1078c). Another fragment
from Plutarch suggests that Arcesilaus argued against Zeno's causal
theory of perception (Fragment 215a). And Sextus reports that
Arcesilaus also objected to Zeno's conception of belief as assent to an
impression, 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 of
condition [c] of the Stoic definition of the cognitive impression, it
seems possible to trace a definite strategy behind Arcesilaus'
arguments: he argued against Zeno's empiricist presuppositions by
deploying Platonic objections and theories (see Schofield 1999,
Trabattoni 2005, Vezzoli 2016, and von Staden 1978). One might
conclude, as some did in antiquity, that Arcesilaus therefore had a
hidden objective of undermining Stoic or Epicurean empiricism in favor
of Platonic doctrine (see Sextus *Outlines of Pyrrhonism*
1.234). But Arcesilaus' method implies that he would argue
against Platonic doctrines as well, if anyone proposed them. So if he
did hold the view that nothing can be known, it seems more plausible to
think that he held it due to the success of his arguments against all
conceptions of knowledge, rather than solely as the conclusion of an
argument relying on a particular epistemological theory. Cicero's
account, then, may give only a partial story of the grounds of
Arcesilaus' skeptical views.




The second problem with the interpretation of Arcesilaus'
skepticism in *Academica* 2.66-7 & 2.77 is that it
risks self-defeat. The problem lies not in knowing that nothing can be
known, since, on one account
(Cicero *Academica* 1.45), Arcesilaus, unlike
Socrates, explicitly disclaimed such second-order knowledge. It lies
rather in believing that nothing can be known in conjunction with the
belief that it is irrational to hold opinions in the absence of
knowledge. If the former is true, it is irrational (and so one ought
not) to believe the premises of the arguments that support both
*inapprehensibility* and *universal suspension*.


## 4. *Inapprehensibility* and *Universal Suspension of Assent*




There are two approaches to resolving this second problem, that
accepting *inapprehensibility* and *universal suspension*
may be self-defeating. The *NRNB* view takes a negative route,
denying that Arcesilaus was committed to *inapprehensibility*
and *universal suspension*, at least as a prescriptive claim
about the irrationality of assent (see [7] in sect. 3). By contrast,
the *RNB* and *NRB* views positively ascribe
*inapprehensibility* and *universal suspension* to
Arcesilaus, but they maintain that his acceptance of them is not
explained in terms of rational belief of the sort which would lead a
Stoic convinced by Arcesilaus to a self-defeating position (see sect.
2).


### 4.1 The *Non-Rational Non-Belief* interpretation




The *NRNB* view of Arcesilaus argues that he was *not*
committed to *inapprehensibility* and *universal
suspension*, as a *prescriptive* claim about the
irrationality of assent (see [7] in sect. 3). On this view, the two
sources for the anti-Stoic arguments still imply that Arcesilaus was
'committed' to *universal suspension*, but this is
understood as the *descriptive* claim that the skeptic does not
assent to anything due to the balance of opposing arguments; and he was
committed to it only in the sense that he acted in accordance with his
unreflective impressions (see sect. 5.1 below). Thus, there is no
conflict between the anti-Stoic sources, Sextus and Cicero, and those
that report that Arcesilaus' *universal suspension* is
caused by the equipollence of arguments without mentioning his
criticism of Stoic epistemology (viz., Diogenes Laertius 4.28, Cicero
*Academica* 1.45, & Sextus *Outlines of Pyrrhonism*
1.232).




This interpretation takes Sextus to imply that Arcesilaus'
commitment to a descriptive version of *universal suspension* is
prior to his anti-Stoic argument (*M*. 7.156-7),
outlined above in sect. 3 (see e.g., Ioppolo 2002; 2009). In this
argument he holds that the Stoic who concedes the non-existence of
cognitive impressions is forced to conclude that it is rational to
'withhold assent' ('*asugkatathetein*')
about everything (see [10] below). This conclusion is sufficient to
oppose the Stoic thesis that some assents are rational. The full
version 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., assent
to 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 to
the suspension of judgment ('*epoche*')
indicates, on this account, a commitment to *epoche* that
is independent of Stoic notions like assent and the irrationality of
holding opinions, because it is reached only through the equipollence
of arguments.




The *NRNB* view also interprets Cicero as confirming that
Arcesilaus was committed to the descriptive version of *universal
suspension*, even though Cicero *Academica* 2.66-7
& 77 reports that Arcesilaus was committed to various components of
his anti-Stoic arguments (see sect. 3): that there are no cognitive
impressions, that nothing can be known, that it is irrational to hold
opinions, and that it is rational to suspend assent. Cicero may be
unreliable here, because he is biased by his own, later conception of
radical skepticism, and in his text one may yet find an alternative
view (see Ioppolo 2008): at *Academica* 2.32, Cicero's pro-Stoic
character Lucullus refers to skeptical Academics who concede that
everything is uncertain ('*adela*') without
preferring any views; and these Academics appear to be followers of
Arcesilaus (cf. *Academica* 2.16 & 59). Since these
Academics' suspension of judgment is based on the notion of
uncertainty, which is not necessarily Stoic, their skeptical views do
not depend on an anti-Stoic critique.




However, there are strong reasons not to read Sextus and Cicero as
confirming that Arcesilaus' commitment to a descriptive version
of *universal suspension* is independent of his anti-Stoic
arguments. Even if Arcesilaus developed a notion of suspension
('*epoche*') before his criticisms of the
Stoa, premise [11] above conceptualizes it in Stoic terms. It is true
that Arcesilaus in Sextus *M*. 7.156-7 goes beyond the
point sufficient to oppose the Stoic--viz., that the wise person
does not assent to anything (see [9] above). But he continued the
argument because there is a conceptual difference between not assenting
and withholding assent (see e.g., Friedman 2013), and because
*epoche* refers to the latter. Withholding assent
presupposes a prior examination of evidence and the recognition of an
equipollence among the reasons for competing beliefs. (See also Maconi
1988 and Benatouil 2011.) As for the evidence of Cicero,
even if Lucullus thinks Arcesilaus himself belongs to the group of
Academics who say that everything is non-evident, he also accuses
Arcesilaus of appealing to the authority of Presocratics to promote his
view of *inapprehensibility*, which crucially presupposes Stoic
conditions on knowledge (*Academica* 2.15). So even Lucullus
thinks Arcesilaus' skepticism is related to his anti-Stoic
arguments.




There are further problems with the *NRNB* view, separate
from the issues of interpretation mentioned above. For one, it narrowly
restricts the skeptic to a life of unreflective reaction (see sect.
5.1), and therefore does not seem compatible with the patterns of
rationality and inquiry that Arcesilaus engaged with. Its narrow
restriction on the scope of skeptical action is also overly dogmatic:
were the *NRNB* view true, it seems implausible Arcesilaus would
see the need for a theory of skeptical action, let alone use the
*Stoic* model of non-rational animals.


### 4.2 The *Rational Non-Belief* interpretation




The *RNB* view of Arcesilaus denies that his acceptance of
*inapprehensibility* and *universal suspension* is
explained in terms of *belief* in the premises and hence in the
conclusions of his arguments. Rather, on this account Arcesilaus
guides his rational activity by something like a supposition or
hypothesis--a set of notions deployed variously in Plato's
dialogues, Theophrastus' dialectic, and geometrical theory (see
Schofield 1999 and Thorsrud 2018; cf. Benatouil & El
Murr 2010). Even the Stoics distinguished hypotheticals from
assertions and arguments, such that one can accept hypotheses and what
follows from them without asserting them (see Barnes 1997). Arcesilaus
could have adapted this kind of theory to account for the rational
activities of the skeptic. Accounts of impression and assent also
afford a distinction between beliefs and belief-like imaginings such
as suppositions, which may then take the place of beliefs in chains of
inference. This distinction allows for a *reasoned* commitment
that falls short of assent (see Striker 1980, Bett 1990, and
Reinhardt 2018). Arcesilaus, on this view, supposes that we ought to
live without realist commitments that fix our view of the world. His supposition may have been based on
premises--some of which he shared with Zeno--as well as on a
generalization from his philosophical experience, after repeatedly
finding 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 hypotheticals
without a large web of background beliefs (see Frede 1979 and Bett
1989). Without them, the skeptic seems unable to decide which
hypotheses to suppose and when to suppose them. And even if such a life
is possible, it is not clear how it would be practically
distinguishable from, and so preferable to, a life based wholly on
belief. If the skeptic regards as hypothetical the very same things we
ordinarily believe, then skepticism seems unmotivated. (See Thorsrud
2010 and Perin 2013 for other objections.) Perhaps one could defend
the possibility of a radically skeptical life of this kind by saying
that, while its development requires starting with beliefs, over time
an increasing number of background beliefs may be substituted with
hypotheses, and that the benefits of the skeptical life are of a
second-order, affecting the ease with which the skeptic can change the
guiding assumptions of her life.


### 4.3 The *Non-Rational Belief* interpretation




The *NRB* view instead argues that *universal
suspension* isn't opposed to beliefs *per se*, but only to
beliefs justified through philosophical theory or reasons generally.
The Stoics maintain that the mind is essentially rational, so that its
assent is necessarily reason-responsive (see Coope 2016).
Arcesilaus' skepticism, on this view, challenges the rationalist
presupposition that belief is necessarily and explicitly grounded in
reason. This doesn't preclude that Arcesilaus found himself--as
a result of the inadequacy of the arguments for any position, and of
the equally convincing arguments against it--with the belief
that nothing can be known. Thus, *inapprehensibility* is neither
the conclusion of a deductive argument relying on a theory of knowledge
or of our cognitive faculties, nor an inductive inference from prior
investigations; it is not a theoretical or even rationally warranted
belief, but just the way things strike him (see Cooper 2004 and
Thorsrud 2009).




But in the case of *universal suspension*, it seems that the
view that it is irrational to hold unwarranted beliefs is
held--at least in part--on the basis of a theoretical belief
that knowledge is very important to acquire and that mere belief is to
be avoided. Cicero, for instance, stresses that Arcesilaus agreed with
Zeno that it is irrational to hold opinions, i.e., inadequately
warranted assents (premise [6] in sect. 3, above); and Sextus suggests
that he thought that individual cases of suspended
belief--presumably in the light of inconclusive
arguments--were good (*Outlines of Pyrrhonism* 1.233). And
the view that it is irrational to hold mere beliefs (that is,
opinions) depends on a further set of epistemological beliefs about
the nature of belief and knowledge. If Arcesilaus was not rationally
committed to any set of assumptions about the nature and requirements
of rationality or about belief and knowledge--which he ought not
to be, given that he had argued against the various views on offer,
and hence, *ex hypothesi*, suspended belief about them--it
doesn't look like he can believe that one ought not to take beliefs to
be justified.




The *NRB* view thus takes *u**niversal
suspension* to be a belief that is not rationally warranted, as
well as the views on which it causally depends. That is, Arcesilaus
began inquiry motivated by a pre-theoretical belief, that philosophical
knowledge is important and mere belief inadequate. And his repeated and
extensive investigations left him with the realization that even these
regulating assumptions of his philosophical practice have failed to be
warranted and that no beliefs are justified.




On this view, the radical skeptic has beliefs but doesn't take them
to be justified. This proposal raises problems, too (see Burnyeat
1983). It seems that a large part of being a rational agent is to
exercise some control over one's beliefs. Since this control takes the
form of a responsiveness to reasons, it does not seem possible for
rational agents to give up practices of justification. A related
objection is to maintain that even having beliefs, which involves the
use of concepts, is necessarily responsive to reasons (see Williams
2004). To have a belief, according to this view, requires making a
conscious inference about the proper use of concepts, and conscious
inferences are made in virtue of reasons. One may respond that the
skeptic isn't precluding herself from a responsiveness to reasons but
rather lacks confidence in them, and that such rationalist theories of
agency and belief are stricter even than the Stoics', against
which Arcesilaus argued (see sect. 5 below).


## 5. The practical criterion




The third doctrine we might ascribe to Arcesilaus on the basis of
his sources is a so-called practical criterion, i.e., a theory that
makes action without assent possible (see [iii] in sect. 2).
 Arcesilaus' argument for a 'practical
criterion' responds to two Stoic objections of
'inaction' (*apraxia*). The first, found in
Plutarch, is that action is impossible without assent, since action is
caused by assent to an impression of something suited to the agent's
nature, i.e., '*oikeion**'* (*Against
Colotes* 1122a-d; cf. Cicero *Academica*
2.37-8). The second objection, reported by Sextus, is that a good
or successful life is impossible without assent, since a good life
requires action based on knowledge of what is good and bad, and hence
assent (*M*. 7.158; cf. Cicero *Academica* 2.39).
Arcesilaus' reported replies to these objections are brief, and
accordingly difficult to interpret (see Bett 1989). His counter to the
first objection is the suggestion that action is possible without
assent, since even on the Stoic account animal action is triggered
directly by their impressions of something *oikeion*: the
addition of assent, and so a belief that the object is in fact
naturally suited to the agent*,* is redundant and liable to be a
cause of error. In response to the second objection, Arcesilaus argued
that the person who suspends assent universally will successfully guide
their 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 to *inapprehensibility* and/or *universal suspension*.


### 5.1 The *Non-Rational Non-Belief* interpretation




Proponents of the *NRNB* view take the argument of Plutarch
to give a general theory of action that supports universal
suspension of judgment as a natural reaction to equally balanced
arguments. On this theory all actions are merely impulsive, i.e.,
caused just by impressions of what appears suitable
('*oikeion*'). Since the skeptic doesn't make
judgments, the only sense in which she is committed to her impressions
is that she acts on them. It is unclear how this is compatible with the
evidence of Sextus on 'the reasonable', where the skeptic
considers reasonable justifications in deciding what to do. But some
advocates of *NRNB* combine the two so that a class of impulsive
actions count as voluntary if, after their performance, one can
reasonably justify them as successful (e.g., Ioppolo 1981; 1986; 2000).




Even allowing for this attenuated sense of the voluntary, it is
unclear why Arcesilaus would come to accept this impulsivist theory of
action, if it were true: since--as the theory
maintains--theory doesn't inform action, it is difficult to
explain theoretical commitments solely in terms of what appears suited
to an agent (see Maconi 1988, Trabattoni 2005, and Vezzoli
2016). An *NRNB* reading of 'the reasonable'
therefore concedes that Sextus may have elided important details (see
Ioppolo 2018).


### 5.2 The *Rational Non-Belief* interpretation




The *RNB* view opens up a more promising way to read the
brief counter-arguments in Plutarch and Sextus as a positive theory of
Arcesilaus. His counter in Plutarch is that action isn't always caused
by occurrent beliefs--we sometimes act through habit, or by
instinct. By itself, this doesn't go very far, however, since the
Stoics will have objected that, even if this were possible, this
account couldn't describe the voluntary and responsible actions of a
rational agent. (The Stoics defined responsible or voluntary action in
terms of assent, since this was the mechanism through which our
rationality acts on the world.) But one can read the counter-argument
in Sextus as supplementing that response: there is space for
rationality and responsibility, on this view, in the production of the
impressions or thoughts motivating us when we act. We can act in
accordance with what strikes us as the reasonable thing to do upon
reflection, but still refrain from assent, i.e., refrain from forming
the belief that this is the right thing to do.




There are two problems facing this interpretation of 'the
reasonable'. The first is that it does not look to be supported
by the evidence to which it appeals. Sextus, the source for the notion
of 'the reasonable' as the criterion, says that Arcesilaus
and his followers did not define a criterion and that, when they
seemed to, they did so "a counterblast to that of the
Stoics" (*M*. 7.150, Bury trans.). (Sextus' later
account of Arcesilaus in another work is also incompatible with his
hypothesizing such a theory; see *Outlines of Pyrrhonism*
1.232-3.) And Cicero and Numenius, our other sources for the
view that Arcesilas was committed to *inapprehensibility*
and *universal suspension*, do not mention his adoption of a
practical criterion--in fact, in both authors it is suggested
that Arcesilaus did not offer a position on how one might live without
assent, and that Carneades significantly revised the Academic position
in 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 explicitly
demand that Arcesilaus' practical criterion was a dialectical
ploy, the argument Arcesilaus used to support it makes the most sense
if it is construed dialectically. The argument he gives is something
like this (Sextus *M*. 7.158):


13. a good life depends on practical wisdom;
14. practical wisdom consists in a disposition causing right or
successful actions;
15. right or successful actions are those that have a reasonable
defense (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 that
there is no other evidence that Arcesilaus was committed to premises
[13] through [16], and they are also ones that Arcesilaus may have
argued against, since it is reported that he argued not just against
the Stoic theory but against all ethical views (Philodemus *Index
Academicorum* 18.40-19.9, Diogenes Laertius 7.171, Numenius
fr. 25.154-61, cf. fr. 25.41-5).




The second, more pressing difficulty is that, although these premises
are adapted to the Arcesilean context in which nothing can be known
and the wise person does not assent to anything, they are manifestly
variants of the Stoic theory. The Stoics claimed that a good life is
the result of performing 'appropriate
actions'--defined as "those that, once done, have a
reasonable defense"--from a disposition of wisdom, i.e.,
knowledge of what is good, bad and neither. But if nothing can be
known, as Arcesilaus has already argued ([5]-[7] in sect. 3,
above), the wisdom of the sage consists in not having any
beliefs. This disposition will still allow the sage to perform
appropriate actions, however, if, as the Stoics claim, they are
defined by reasonable defenses or justifications. The connection
between performing such actions through a wise disposition and success
is, Arcesilaus suggests, something that the Stoics can't deny, because
they agree that opinion is the cause of error (this is the
justification for premise [6] in sect. 3, above). Hence, the perfect
exercise of our rationality--reflection without assent, as
Arcesilaus has argued--will lead us to find the action that is
appropriate to us as rational animals, i.e., the reasonable thing to
do, and this guarantees success. Arcesilaus therefore employs the
Stoic definition of appropriate action to defend acting on views that
are reasonably justified. But, for the Stoics, what is reasonably
justified is what conforms with the sage's knowledge of what is
good, bad, and neither. Arcesilaus, it seems, cannot borrow his
opponents' theory without also accepting the possibility of
knowledge.


### 5.3 The *Non-Rational Belief* interpretation




The *NRB* view can instead deny that Arcesilaus was
personally committed to defending the life of *universal
suspension* against Stoic counterattack. The Stoics pointed out
that Arcesilaus' subversive argument for the rationality of
universally suspending assent cannot be true, because it makes action,
or at least rational and virtuous action, impossible--but these
are plainly possible (cf. Cicero *Academica* 2.37-39). But
even if this objection did not target his own skeptical view,
Arcesilaus was bound by his method to counter it. Hence it is
unreasonable to think that he was invested in rationalizing the life of
the skeptic with a theory of action (see Stopper 1983; for a
different 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 of
Arcesilaus' skepticism is how to reconcile his method with his
skeptical commitments, and sections 4-5 set out three accounts of
how his commitments are compatible with his method. A further question
relates to the purpose of Arcesilaus' philosophical activity.
Competing histories of Arcesilaus' intentions in Cicero's
*Academica* offer different answers (see Allen 2018): at one
point Cicero suggests that Arcesilaus adopted a Socratic method
*after* he accepted *inapprehensibility* and
*universal suspension*, in order to facilitate suspension of
assent (*Academica* 1.44-45; cf. Sextus *Outlines of
Pyrrhonism* 1.232); but elsewhere he says that Arcesilaus'
aim in questioning Zeno was to discover the truth (*Academica*
2.76; cf. Cicero *On the Nature of the Gods* 1.11). So
in question is whether Arcesilaus' method was
in the service of inquiry--independently of his commitments to
*inapprehensibility* or *universal suspension*--or
a revival of a Socratic methodology that only reflected skeptical
conclusions he already reached.




An argument in favor of the latter is as follows (see Gorler
1994): if Arcesilaus indeed shared the views that knowledge is
impossible and that holding opinions is irrational--as both the
*RNB* and *NRB* interpretations say--then he could
not have genuinely been in the business of inquiry, which aims at
knowledge of the truth; hence the only motivation for dialectical
argument Arcesilaus might be left with is the promotion of
*universal suspension*. But this argument ignores the context
from which Arcesilaus' skeptical views emerged and the effects
they could reasonably be expected to have had on his philosophical
practice.




On the *RNB* view, the Academic skeptic, at the start of her
philosophical career, inherits a rational method of inquiry, as well as
guiding views about belief and knowledge. But her inheritance is so far
untested (at least by her). As she goes about putting it to work, she
might at first believe that her method and its norms help her to get at
the truth. But she then finds that by arguing in accordance with those
norms she is wildly successful at combatting any and all positions. She
therefore comes to suppose on rational grounds--which may
include particular arguments against Stoic cognition, the inadequacy of
all non-skeptical theories of knowledge, and her experiences in
argument generally--that the norms cannot successfully guide her
to truths. But she doesn't quit her life of inquiry because her
skeptical view of the inadequacy of her method depends on that very
method; it makes little sense for her to act on a view that rejects its
own grounds. Instead she continues to inquire, now treating her
inherited norms and guiding views about belief and knowledge only as
hypotheses rather than as given. On the *RNB* view, therefore,
Arcesilaus' skepticism was self-defeating only insofar as it
could not justify abandoning reason.




A similar story can be told with the *NRB* view. The skeptic
looks for the truth, on the assumption that obtaining it is of crucial
importance for her life. But since she consistently fails to find it,
it begins to strike her that perhaps she never will. Perhaps, it was
not, after all, so important for her life to have it: maybe mere
belief 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 it
would only be correct to give it up if it actually is true that mere
belief is all she needs--but this is something that her arguments
don't warrant, any more than they warrant the opposite
conclusion. An *NRB* view, then, suggests that
Arcesilaus' beliefs in the importance of knowledge and the
inadequacy of opinion were explicitly non-rational, in the sense that
he was not persuaded that they were warranted by a rational argument
or theory, or even by the extensive arguments he devoted his life
to. He believed that he hadn't found knowledge and that it is
irrational to assent to anything without knowledge, but realized, as a
result of the unrestricted application of his Socratic method, that
there were strong reasons against these beliefs. He was thus not in a
position to give his rational assent to the belief that it is
irrational to hold opinions--he just found that that was how
things striked him, i.e., that's what he believed. The Academic
skeptic, on this view, is someone whose sustained but pre-theoretical
commitment to rational investigation undermines her confidence in
rationality. The result is not a negative theory--e.g., the
theory that we can't acquire knowledge owing to the limitations of our
cognitive or rational capacities--but a pervasive lack of theory
sustained by a dialectical method.




If either of these stories is correct, we don't need to deny
Arcesilaus seached for the truth, and the basic philosophical puzzle
about his radical skepticism is not whether it is possible to live
without rational beliefs, but whether it is possible to be committed to
rationality 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 into
account both his reputation as a master dialectician who deployed
Socrates' method ruthlessly against his philosophical
contemporaries, and his notorious advocacy of
*inapprehensibility* and *universal suspension*. Given
the contradictory nature and scarcity of the evidence, it is perhaps
not surprising that modern critics do not agree about the success of
the 'dialectical' or various 'doctrinal'
interpretations of Arcesilaus or about the consistency of the very
different kinds of skepticism the latter propose. But further progress
is not ruled out, since it is open to us to offer more sophisticated
philosophical elaborations of those forms of skepticism and to test
their historical plausibility by appealing to the diverse, but better
attested traditions in the later Academy.