Ancient Skepticism (Part 5 – End)

4.4 Sextus Empiricus

Sextus’ (ca. 160–210 CE) epithet, Empiricus, indicates that he—at least at some point in his life—belonged to the empiricists, a medical school (on the relationship between medicine and skeptical therapeutic argument, cf. Voelke 1990; cf. Svavarson 2014 for a brief conspectus of Sextus’ philosophy). The empiricist medical school argued against rationalistic tendencies in medicine (Frede 1990; Allen 2010). Rationalism in medicine aims to give causal explanations as a basis for therapies. Empiricism, on the contrary, confines itself to observation and memory. Somewhat confusingly (considering his name), Sextus discusses differences between Pyrrhonism and empiricism, and says that skepticism is closer to medical methodism than to empiricism (Allen 2010). Methodism follows appearances, and derives from them what seems beneficial. No explanations are attempted, no underlying substances postulated, and no regularities assumed—these are some of the rationalistic methods that both methodism and empiricism argue against. Methodism also makes no statements to the effect that such explanations cannot be given, or that underlying substances and regularities do not exist, as Sextus says empiricism does (SE PH 1.236–241).


Sextus’ writings are traditionally divided into two groups. The Outlines of Pyrrhonism [PH] consists of three books. PH 1 is the only general account of Pyrrhonism that survives. PH 2 and 3 discuss questions of logic, physics, and ethics. The other writings are summarily referred to, traditionally, as Against the Mathematicians [M]. In fact, they oppose not just mathematical, but also other theorists: the title really means Against the Theoreticians, or Against the Learned (Bett 2012). In a sense, only M 1–6 should go by that title. It is a complete work, and M 7 does not seem to be its continuation (Bett 2012, “Introduction”). M 1–6 discuss grammar, rhetoric, geometry, arithmetic, astrology, and music theory. They argue against theoretical ‘learning’ in these fields. M 7–11 discuss core questions of the three philosophical disciplines, logic, physics, and ethics, and could plausibly be referred to as Against the Logicians (M 7–8), Against the Physicists (M 9–10), and Against the Ethicists (M 11). Scholars disagree on whether M is earlier (Bett 1997) or later than PH (Janacek 1948 and 1972). Scholars also disagree on whether we can evaluate different strands of skepticism within Sextus as more or less sophisticated. Those who consider PH as later often do so because they think it shows greater philosophical sophistication, either by avoiding claims that a certain matter cannot be known (sometimes described as negative dogmatism), as found in M 1–6 and M 11, or by streamlining discussions from M 7–10 (Bett 1997; Brunschwig 1980).

These questions are complicated further by Sextus’ attempt to incorporate diverse material, such as different sets of Modes, into his skepticism (for the view that the different sets of modes are part of an integrated philosophical approach, cf. Powers 2010). Arguably, two kinds of consistency are at work in Sextus’ writings. On the one hand, Sextus aims at the consistency of one philosophical outlook. On the other hand, he aims at the consistency of having a response to every objection. These two aims overlap greatly, but they can also come apart. A given argument might refute a particular critic. This argument may go back to various earlier versions of Pyrrhonism. Similarly, the critical objection that is refuted may be traced to dogmatic theories formulated over the course of several centuries. As a result, a given argument in Sextus may be effective against a given objection he has in mind. It may thus preserve consistency in the sense of leaving the skeptic unharmed by dogmatic criticism. But at the same time, this argument may have implications that are in tension with the way in which Sextus explains skepticism in other passages. Such tensions are particularly important with respect to the way in which Sextus uses core concepts. For example, it is not clear that Sextus uses the notion of appearances (phainomena) in a consistent fashion (PH 1.8–9; 1.15; 1.22; for the view that Sextus employs the notion consistently throughout, see Barney 1992). At times, he draws on the contrast between appearances and thoughts (noumena). But for the most part, the term refers to all cases where something seems so-and-so to the skeptic, either perceptually or in thought. In some contexts, Sextus draws on the idea that appearances are impressions, invoking the dogmatic assumption that impressions are passive. In other contexts, he does not envisage appearances as entirely passively experienced (Vogt 2012b).

It is thus no surprise that the interpretation of Sextus’ Pyrrhonism is quite controversial. This applies in particular to the question of whether the skeptic has any beliefs, or beliefs of any kind. In the past 30 years, scholars have paid attention to this question more than to any other interpretive issue. Insofar as the texts may contain different strands of Pyrrhonian argument, exegesis is to some extent shaped by the philosophical interests we bring to the texts. Two ideas are particularly prominent here. First, some scholars find in Sextus an account of action that challenges standard ancient and modern theories of agency. These theories might portray ordinary agents as all-too-rational, as if every action involved a belief that such-and-such is good. Scholars explore how far we can draw on Sextus, asking whether a life guided by appearances (as Sextus says the skeptic’s life is) might after all be rather ordinary (Frede 1979 [1997]). Second, one might on the other hand embrace those aspects of Sextus’ texts that make Pyrrhonism look radically different from ordinary life. From this perspective, Sextus’ writings invite reflection on the question of whether it would be possible to live without belief (Burnyeat 1980 [1997]; Barnes 1982 [1997]; Burnyeat 1984 [1997]).

PH 1, which figures most prominently in scholarly discussions, is a tour de force. Sextus gives a general account of what skepticism is, including skeptical investigation, suspension of judgment, the skeptic’s end, action, and language; he gives lists and illustrations of various sets of Modes; he explains the so-called skeptical formulae (phônai), such as “I determine nothing,” “non-assertion,” “maybe,” and so on; and he compares skepticism to relevantly similar philosophies.

Sextus emphasizes that the skeptic is an investigator. Others either arrive at theories (dogmatism) or at claims about inapprehensibility (negative dogmatism—that the matter investigated is beyond one’s capacity to decide, and so is unknowable). But the skeptic continues to investigate (PH 1.1–4). Investigation is described as setting appearances and thoughts into opposition (PH 1.8) (Morison 2011 offers a reconstruction of skepticism that takes its starting–point from this description), and as the application of the various sets of Modes (PH 1.36–186). Skepticism does not have teachings, but it is a philosophy. Many of the thoughts the skeptics arrive at are expressed in the skeptical formulae (PH 1.13–15; 187–209). The starting–point (archê) of skepticism is divergency—anômalia. The proto-skeptics are disturbed by the discrepancies they encounter, and begin to investigate (PH 1.12). They hope to gain quietude by settling what is true and what is false. But then they have a surprising experience. Encountering disagreement where several views appear to be of equal weight (isostheneia), they find themselves unable to decide things, give up, and experience tranquility (ataraxia) (Striker 1990 [1996]; Nussbaum 1994). The skeptic’s end (telos) is tranquility in matters of belief (kata doxan) and moderate affection (metriopatheia) in matters that are forced upon us (PH 1.25–29). That is, skeptics can free themselves from those kinds of turmoil that come with holding beliefs. They cannot free themselves from freezing, thirst, or pain. But they suffer less than others, for they do not add the belief (prosdoxazein) that, for example, pain is bad. The skeptic must explain how, without belief (adoxastôs), they can be active. Sextus says that skeptics follow appearances, and that is, that they adhere to the fourfold ways of life (PH 1.21–24). Nature supplies them with perception and thought; necessary affections compel them (for example, thirst guides them to drink); they go along with traditions and customs; and they can do technical things by having been instructed in skills. The notion of appearances is also central to Sextus’ account of how the skeptic can speak. Without making assertions, a skeptic reports (apangellein) like a chronicler (historikôs) what appears to them now (PH 1.4).

I shall discuss the following aspects of Sextus’ skepticism: (i) investigation, (ii) concepts and inference rules, (iii) belief, (iv) the formulae, (v) appearances, (vi) language, (vii) action, and (viii) the so-called special arguments (that is, arguments that do not explain the nature of Pyrrhonism, but engage with specific dogmatic theories in logic, physics, and ethics).

(i) Investigation. Investigation must aim at discovery of the truth, otherwise it is not genuine investigation. However, a skeptic seems to mechanically apply the skeptical Modes, in order to generate suspension of judgment and tranquility. It seems as if the skeptics do not genuinely aim at the truth (Palmer 2000; Striker 2001; Perin 2006), though they claim to keep on investigating. Note that this objection, unlike the other problems central to contemporary engagement with ancient skepticism, was not raised in antiquity. If ancient skepticism is approached in the context of the larger study of ancient philosophy, we might first of all note that the skeptics in a sense agree with Socrates, Plato, Aristotle, Epicurus, and the Stoics. All these philosophers defend, in so many formulations, a life of reason, of contemplation, of wisdom, or of inquiry as the best or at least a very good human life (on affinities between the skeptics’ commitment to inquiry and Aristotle, cf. Olfert 2015). The objection that skeptical inquiry seems insincere, then, may not have come up in antiquity in quite the way in which it is discussed today because a commitment to inquiry would be common ground among most philosophers. Further, we might observe that aiming at the truth includes two aims: to accept truths, and to avoid falsehoods. The Modes are tailored to keep us from assenting to something that could be false. Insofar as the skeptic’s effort to avoid falsehoods expresses a valuation for the truth, the skeptic might be a genuine investigator (Vogt 2012a, ch. 5; Olfert 2014).

A related objection calls into question the actual practice of skeptical inquiry. Does Sextus rely on the assumption that, in any given case of putting several arguments into opposition, these arguments are equally persuasive for the skeptic? This seems unrealistic: at least in some cases, skeptical inquirers are bound to be more strongly attracted to one view than to another. How then do they arrive at suspension of judgment? One skeptical strategy is to remind oneself that additional arguments will be formulated in the future (PH 1.33–34, 89, 96–97; 2.38–41; 3.233–34). Another strategy is to consider that different arguments are persuasive to different people (Svararsson 2014). Relatedly, skeptics may find themselves in a position comparable to a student who takes a seminar on freedom and determinism: it is possible to be more attracted to one view rather than another, and at the same time be aware that as far as the arguments are concerned, there is unresolved disagreement among several views, to the effect that neither of the views seems compelling in ways that warrant assent (cf. Vogt 2012a, ch. 5, on how the skeptical expression “as far as the argument is concerned” bears on this question; for general discussion of this expression, cf. Brunschwig 1990).

(ii) Concepts and rules of inference. If skeptics do not assent, then how can they understand the terms philosophers use (M 8.337–332a)? Even more radically, how can they even think (PH 2.1–12)? This objection, which Sextus says is continually raised against the skeptics, proceeds on the assumption that possession of concepts involves the acceptance of assumptions. For example, in order to examine a given theory of proof, the skeptic must have a notion of what proofs are. This involves assumptions: for example, the assumption that a proof contains premises and a conclusion. Sextus’ response to this objection invokes the Epicurean and Stoic theories of preconceptions. Human beings are not born with reason (Frede 1994, 1996). The acquisition of reason is a nature-guided process of concept acquisition. At a given age, children have completed this process. They have become rational, which means that they can perceive and think in a conceptual way. Only now, they have rational impressions to which they can assent. The acquisition of preconceptions did not involve assent, simply because the child was not yet rational (Brittain 2005).

Sextus invokes dogmatic ideas about the acquisition of reason (or: the abilities of conceptual thought) in his response to the Apraxia Charge (PH 1.23–4). Skeptics are, first of all, active because nature has equipped them with perception and thought (Vogt 1998, 2010). More generally, the skeptics’ ability to think and investigate depends on the fact that they have acquired concepts as part of growing up. This process did not involve assent, and accordingly, Sextus argues that the skeptic’s ability to think does not violate suspension of judgment (cf. Brunschwig 1988; Vogt 2012a ch. 6; Grgic 2008; Fine 2011). It is conceivable, though, that the skeptic’s ability to understand involves some knowledge, namely a kind of knowledge that does not entail any belief (Corti 2009, part III; Corti 2015). This option appears counterintuitive given today’s premises in epistemology, according to which someone who knows that p also believes that p. The relevant notion of belief in skeptical discussions, doxa, as well as the relevant ancient notions of knowledge, however, may behave quite differently (cf. Vogt 2012a and Moss and Schwab forthcoming on belief; Burnyeat 1980c, Frede 2008 and Schwab 2016 on knowledge). Insofar as doxa is an inherently deficient activity and attitude, and insofar as knowledge is conceived in elevated ways, knowledge without belief is a rather intuitive option within ancient epistemology. If understanding concepts and arguments involves knowledge that does not entail beliefs, the skeptics may be taken to have such knowledge. Modern critics raise the further question of whether the skeptic must endorse logical laws (such as the Principle of Non-Contradiction) and rules of inference. In particular, they ask whether a skeptic is committed to the logical validity of the conditionals they formulate when arguing against the dogmatists (Sorensen 2004). Sextus records no ancient version of this complaint, and accordingly no direct response.

(iii) Belief. Bury, in his Loeb translation, translates adoxastôs as “undogmatically,” for example, when Sextus speaks (PH 1.15) of skeptics as saying that “nothing is true.” This translation suggests that Sextus bans dogmatism from the skeptic’s life, where this still leaves room for other, non-dogmatic beliefs. But adoxastôs means non-doxastically or ‘without belief’ (cf. Burnyeat 1980 [1997]). As noted above, the skeptic’s end is tranquility in matters relating to belief—kata doxan. A skeptic lives adoxastôs. And even more confusingly, the skeptics assent adoxastôs, when they act.

Contemporary interest in Pyrrhonian skepticism was much spurred by Michael Frede’s paper “The Sceptic’s Beliefs” (1979 [1997]). Frede argues that ancient skepticism was traditionally dismissed too easily as vulnerable to the Apraxia Charge, the charge that, without belief, the skeptic cannot act. The skeptics seem to be confident that they have replies to this objection. Thus, it seems uncharitable not to look closely at these replies. Further, insofar as these replies respond to the charge that without belief one cannot act, we should focus on what the skeptics say about the role of belief in their lives. Frede cites PH 1.13, and claims that in this passage we find a distinction between two kinds of belief:

When we say that the skeptic does not dogmatize, we are not using ‘dogma’ in the more general sense in which some say it is dogma to accept anything (for the skeptic does assent to the experiences forced upon him in virtue of this-or-that impression: for example, he would not say, when warmed or cooled, ‘I seem not to be warmed or cooled’). Rather, when we say he does not dogmatize, we mean ‘dogma’ in the sense in which some say that dogma is assent to any of the non-evident matters investigated by the sciences. For the Pyrrhonist assents to nothing that is non-evident. (PH 1.13; trans. Burnyeat (1984) [1997] with changes)
Following Frede, several scholars focus on PH 1.13 when discussing skeptical belief (with the notable exceptions of Barnes 1980 [1997] and Barney 1992). They take it to be obvious that, in this paragraph, Sextus distinguishes between two kinds of belief, one which he bans from the skeptic’s life, and one which he allows into the skeptic’s life. Barnes (1982 [1997]) employs a distinction between rustic and urbane skepticism. The rustic skeptic suspends on all matters. The urbane skeptic suspends on scientific matters, but holds ordinary beliefs. The clause “non-evident matters investigated in the sciences” in PH 1.13 might be taken as a point of reference for the urbane interpretation. However, Barnes points out that this cannot be right. Everything can be considered as a non-evident matter, even such things as whether honey is sweet.

Against Barnes, Frede argues that the relevant distinction must be drawn between two kinds of assent, such that “having a view involves one kind of assent, whereas taking a position, or making a claim, involves another kind of assent, namely the kind of assent the sceptic will withhold” (1984 [1997], 128). Sextus characterizes skeptical assent in three ways. He speaks of forced assent (PH 1.23–24), involuntary assent (PH 1.19), and adoxastôs assent (PH 2.102). Frede does not explore the details of how Sextus uses these notions. The core of his proposal is that Sextus allows for a kind of assent that does not involve a claim as to how things are in actual fact.

In (1979 [1997]), Frede is predominantly concerned with the skeptic’s reply to the Apraxia Charge. In (1984 [1997]) his focus is on skeptical pronouncements such as “nothing can be known.” His distinction between two kinds of assent, and accordingly two kinds of belief, is explored with respect to such sentences. Frede writes that “[t]o be left with the impression or thought that p […] does not involve the further thought that it is true that p” (133). This is the sense in which, on his interpretation, the skeptic might think “nothing is known.” The thought counts as a belief, but not as a claim that, in actual fact, nothing is known by anybody. Contrary to Frede’s interpretation, one might argue that to believe simply is to hold true, at least according to the notions of belief that the skeptics invoke in discussions with their contemporary critics (Vogt 2012b). It is thus not clear that Frede’s distinction is genuinely one between two kinds of beliefs (Burnyeat 1980 [1997]). Perhaps it is a distinction between two different propositional attitudes, only one of which is belief. As Striker (2001) points out, there is a danger that debates over this issue become merely terminological. We might thus draw a distinction between two issues. It is one thing to disagree with Frede on what should or should not be called belief, and another to dispute whether he identifies and characterizes a phenomenon in the skeptic’s mental life. As Frede argues, skeptics find themselves with a rather persistent thought, without having accepted it as true in actual fact. This appears to capture a core element of skepticism: the way in which the skeptic thinks such thoughts as “everything is inapprehensible.”

(iv) The Skeptical Formulae. PH 1.13, the passage in which scholars find a distinction between two kinds of belief, occurs in a chapter entitled “Does the Skeptic dogmatize?” One angle from which we might disagree with Frede is to insist that PH 1.13 addresses the status of the core thoughts of skeptical philosophy, rather than the question of skeptical belief. Consider the rest of the chapter:

Not even in uttering the skeptical formulae about unclear matters—for example, “In no way more,” or “I determine nothing,” or one of the other formulae which we shall later discuss—do they dogmatize (dogmatizein). For if you dogmatize, then you posit as real the things that you are said to dogmatize about; but skeptics posit these formulae not as necessarily being real. For they suppose that, just as the formula “Everything is false” says that it too, along with everything else, is false (and similarly for “Nothing is true”), so also “In no way more” says that it too, along with everything else, is no more so than not so, and hence cancels itself along with everything else. And we say the same of the other skeptical formulae. Thus, if people who dogmatize posit as real the things they dogmatize about, while skeptics utter their own phrases in such a way that they are implicitly cancelled by themselves, then they cannot be said to dogmatize in uttering them. But the main point is this: in uttering these formulae they say what appears to themselves and report their own feelings without any belief (adoxastôs), affirming nothing about external objects. (PH 1.14–15; trans. Annas-Barnes with changes)
When explaining in PH 1.13 how the skeptic does not dogmatize, Sextus may have a particular issue in mind: that some skeptical formulae look like doctrines, and have traditionally been turned against themselves due to their dogmatic surface-structure. For example, “all things are indeterminate” looks like a straightforward dogmatic statement. There is a long history of skeptical attempts to explain the nature of such pronouncements so that they no longer undermine themselves. Sextus arguably mentions several solutions to this problem (PH 1.13–15 and 1.187–209; cf. Pellegrin 2010). In PH 1.15, Sextus identifies the following as his main point: the skeptic merely reports what appears to them. Along these lines, Sextus calls indeterminacy an affection of thought (pathos dianoias; PH 1.198), a state that the utterance “all things are indeterminate” aims to capture. The other solution mentioned in PH 1.14–15 is somewhat more problematic: the skeptical formulae cancel themselves out. That is, one can say them and convey something through them. But then, once one has made a point, they as it were turn back upon themselves and eat themselves up—as fire first burns combustible materials and then destroys itself. This idea became famous through another comparison Sextus uses (invoked by Wittgenstein (1922) 6.54): the skeptical pronouncements are like a ladder that one climbs up; once one is on top, one can throw the ladder away (M 8.481). Scholars disagree on whether Sextus in some sense admits that these statements are self-refuting (McPherran 1987), or whether he defuses their self-refutational structure (Castagnoli 2010, III.14).

(v) Appearances (phainomena). While it is difficult to establish a clear distinction between two kinds of belief in Sextus, there is a comparatively more explicit distinction between two ways of engaging with appearances. Sextus says that, while things appear X to the skeptic, the skeptic does not affirm that they are X. Questions that are traditionally discussed in terms of whether the skeptic has beliefs thus might be addressed in terms of whether the way things appear to the skeptic has a judgment-component. Arguably, “A appears X to me now” can be construed in different ways. Certain examples (say, the way in which it makes sense to say both that the moon appears small and that it appears large) may suggest that appearance can but need not involve something like a judgment (Barney 1992). Some formulations in Sextus seem to insist on a significant difference between the mental activity of something appearing to a cognizer on the one hand, and on the other hand the mental activity that, on the level of language, is represented by assertion. This suggests that, for Sextus, A appearing F to me now does not entail that I hold it to be true that A is F (Vogt 2012b).

(vi) Language. Another approach to the question of whether the skeptic has beliefs looks at skeptical language. Sextus insists that the skeptic does not accept or reject any impression, and associates the absence of these mental acts with the fact that the skeptic does not affirm or deny anything (e.g., PH 1.4, 7, 10). Arguably, we can infer from Sextus’ account of the skeptic’s utterances what Sextus wants to say about the skeptic’s mental states and acts. That is, the question of language immediately bears on the question of belief. The report on Pyrrhonian skepticism in Diogenes Laertius is particularly instructive in this respect. Contrary to scholarly focus on belief in reconstructing skepticism, it barely mentions belief. Discussion of the skeptics’ attitudes is almost entirely conducted in terms of skeptical language and the skeptical formulae (for detailed discussion of the relevant paragraphs, DL 9.74–7, cf. Corti 2015). If Sextus is read in light of the report in DL IX, PH 1.13 may appear to be more of an isolated passage than scholarly debates imply. Sextus too devotes much space to accounts of skeptical expressions and language. It may thus be asked whether scholars should reframe discussions, and pay more attention to skeptical language then they previously have. As of now, there is one monograph on skeptical language, Corti (2009), and one approach to belief that focuses on language, Vogt (1998). Both scholars pursue further ideas put forward by Barnes (1982 [1997]), who compares the skeptic’s utterances to avowals. The skeptic lays open their state of mind, they announce or record (apangellein) it (Fine 2003a). In order to do this, the skeptic must misuse language (Burnyeat 1984 [1997]). Some strategies to avoid assertion are given in the context of the skeptical formulae (“non-assertion,” “I determine nothing,” and so on). (i) Skeptical expressions can be used as signs, which reveal a state of mind (PH 1.187). (ii) Expressions like “ou mallon” (no more) and “ouden mallon” (nowise more) can be used indifferently (in the sense of interchangeably) (PH 1.188). (iii) As is the practice in ordinary language, the skeptic can use expressions elliptically; for example “no more” for “no more this-than-that” (PH 1.188). (iv) People often use questions instead of assertions and the other way around. Similarly, “no more” can be construed as a question: “Why more this-than-that?” (v) The skeptic misuses language and uses it in a loose way (PH 1.191).

In M 1 and M 2, Sextus says that the skeptic goes along with ordinary ways of using language (M 1.172, 193, 206, 218, 229, 233; M 2.52–3, 58–9). This seems to be a key resource in construing skeptical ways of speaking: the skeptic exploits the ways in which ordinary speakers can diverge from grammatically correct speech, and still be understood. Apart from using their skeptical formulae, and apart from conducting philosophical investigations, which they can do in a dialectical mode, referring to theses, arguments, and inferences, the skeptic also has to talk in everyday contexts. It is here where we see best how skeptical utterances are tailored to reveal a state of mind in which nothing is accepted or rejected. Sextus takes great pains to construe his examples of skeptical utterances according to the following schema: “X appears F to me now.” This will generally be understood as an elliptical version of “X appears to be F to me now.” However, Sextus consistently avoids “to be” (Vogt 1998; for the view that “X appears F” avoids reference to external objects, see Everson 1991). The peculiar form of skeptical utterances suggests that Sextus sees a relevant difference between “X appears to be F to me now” and “X appears F to me now.” The former might imply reference to a state of affairs, and an epistemic usage of “to appear” that could be rendered as “It appears to me, that p,” or, “I take it that p.” This, however, would be assertoric: the skeptic would state that it appears to them that such-and-such is the case. But the skeptic’s elliptical utterances about what appears to them aim to be purely phenomenological. They aim to report a condition of the skeptic’s mind, without expressing a judgment of any kind (Burnyeat 1984 [1997]; Annas-Barnes 1985, 23–4; for an assessment of these strategies in terms of modern philosophy of language, cf. Pagin forthcoming). As part of the skeptics’ way of life, language can also be seen as an activity. That is, how the skeptics can speak can be considered a sub–question of how the skeptics can act. Skeptical utterances have been compared to Wittgensteinian confessions, arguably a kind of speech act that is consistent with the skeptics’ avoidance of belief (Corti 2009, Parts I and II). Moreover, the skeptics not only speak. They presumably also understand what others say. A persuasive account of skeptical language must explain both speaking and understanding (Corti 2009, Part III).

(vii) Action. Sextus says that appearances (phainomena) are the practical criterion of the skeptic (PH 1.23–24). By adhering to appearances, the skeptic is prevented from inactivity (anenergêsia). Note that Sextus does not describe the skeptic as performing actions in the sense of dogmatic theory of action, which involves belief and choice (cf. M 11.162–166). Contrary to the Academic skeptic, a Sextan skeptic does not view themselves as a rational agent, who chooses one course of action over another. Sextus claims an active life for the skeptic, but not the life of a rational agent, as conceived by dogmatic philosophers (Vogt 2010).

The skeptic’s forced assent is situated in the domain of action (PH 1.13, 19, 29–30, 193, 237–8). Thirst, for example, necessitates assent, and that means, it moves the skeptic to drink. This kind of assent may be genuinely unrelated to belief-formation of any kind. Rather, forced assent generates the movement of action. But what about more complex kinds of activities, such as applying a medication, or attending a festival? Sextus argues that the skeptic adheres to custom, convention, and tradition, and to what they have been trained to do. In explaining how adherence to appearances in these domains generates activity, Sextus does not mention assent. However, he might have to concede that, like drinking when thirsty, more complex actions also involve some kind of assent. In PH 2.102, Sextus says that the sceptic assents non-doxastically (adoxastôs) to the things relied on in ordinary life. In PH 1.19, he mentions involuntary assent. Accordingly, non-doxastic and involuntary assent may figure in those domains of skeptical action that do not involve necessitation by bodily affections. Non-doxastic assent is, from the point of view of the Stoics, a contradiction in terms, just like forced and involuntary assent. Assent is defined as in our power, and as that by which beliefs are formed. If Sextus intends skeptical assent to be genuinely non-doxastic and involuntary, then it does not have the core features of assent as defined by the dogmatists.

(viii) Logic, Physics, Ethics, and the “disciplines.” The special arguments of the skeptic are directed against particular theories in the three disciplines of Hellenistic philosophy: logic, physics, and ethics. In addition, they address the so-called disciplines, namely grammar, rhetoric, geometry, arithmetic, astrology, and music-theory. Sextus’ treatments of logic divide up into two main topics: sign and criterion (cf. Bett 2005 on signs). This structure reflects central concerns of Hellenistic epistemology as well as of ancient skepticism. Skepticism looks for a ‘decider’ between conflicting appearances and thoughts. A decider could be something evident. Dogmatic philosophers associate the evident with the criterion of truth. For something to serve the role of criterion, it cannot be equally disputed as the matters it helps to decide. Or something non-evident could take on the role of decider. For that to be the case, the skeptics argue, it would have to be conclusively revealed by a sign or proof. If there is no compelling theory of the criterion and no compelling account of sign and proof, then there is nothing that can decide between several conflicting views. Sextus’ treatises on logic thus are not simply a collection of individual arguments against various dogmatic theories. Their main line of thought sketches a route into skepticism.

Sextus’ discussions of ethics also focus on issues that plausibly lead into skepticism. Again, there are two central questions: whether there is anything good and bad by nature; and whether there is an art of life (Bett 2010 and 2011), as the Epicureans and Stoics claim there is. If we could settle what is good and what is bad, some of the most disturbing anomalies would be resolved. If there were an art of life, there would be a teachable body of knowledge about the good and the bad. In both cases, questions that can cause a great deal of puzzlement would be resolved. Sextus’ discussions of ethics are in part famous because Sextus ascribes outlandish and shocking views to the Stoics. As Sextus construes his arguments, the contrast between ‘ordinary life’ and philosophical views leads to suspension of judgment (Vogt 2008a, ch. 1). In the modern tradition, a number of philosophers including Hegel and Nietzsche have engaged with aspects of Sextus’ outlook and in particular with the skeptical adherence to ordinary life (Berry 2010 and forthcoming; Bett forthcoming).

The books on physics discuss god, cause, matter, bodies, mixture, motion, increase and decrease, subtraction and addition, whole and part, change, becoming and perishing, rest, place, time, and number. Notably, god is one of the topics explored in physics. This stands in stark contrast to medieval and early modern discussions, where the quest for knowledge of God often frames and motivates engagement with skepticism (cf. Annas 2011 on the difference between ancient and monotheistic conceptions of divinity and their repercussions for skepticism). The skeptics come to suspend judgment on all central conceptions of ancient physics (Bett 2012). This means, they come to suspend judgment on whether, for example, there are causes, time, place, and bodies (cf. Bobzien 2015 and Warren 2015). Their suspension does not merely mean that they have not yet found a satisfying theory of, say, body. It means that they find themselves unable to say whether there is body (Burnyeat 1997). (On the cumulative force of these arguments, see section 5.4.)

The six books entitled Against those in the Disciplines (M 1–6) have traditionally received less attention. Only in the last few years have scholars begun to explore them with the kind of philosophical subtlety that has been brought to bear in the study of ancient skepticism in recent decades. M 1–6 skeptically examine six fields of study, namely grammar, rhetoric, geometry, arithmetic, astronomy, and music-theory. Sextus begins with an astonishing move. Contrary to his usual strategy of emphasizing the distance between skeptics and dogmatists, he admits that Pyrrhonians and Epicureans share much in viewing standard disciplines as useless (M 1.1–7). Generally speaking, increased attention to M 1–6 may provide additional occasion to modify the long-standing assumption that the Stoics are Sextus’ most important dogmatic interlocutors. Throughout M 1–6, resonances between Epicurean and Pyrrhonian philosophy are remarkably visible (Bett 2018, “Introduction”). Engagement with Epicurean philosophy shapes Sextus’ approach deeply, to the extent that both schools, Stoics and Epicureans, should be considered fundamental points of reference.

After his remarks on how Pyrrhonians and Epicureans take issue with the presumed usefulness of the disciplines, Sextus lays out general arguments, suitable for skeptical examination of any field. He argues that, for there to be a discipline, there must be the matter being taught, the teacher, the learner, and the means of learning. If, however, neither of these things exists, then the discipline doesn’t exist. This is how Sextus proceeds. He argues, or seems to argue, for the non-existence of the disciplines (M 1.9). Already in the very first sentence of M 1, Sextus describes his own approach as one of putting forward counterarguments, a strategy that he mentions repeatedly throughout M 1–6.

These moves give rise to the most contentious question regarding M 1–6. Are these books negatively dogmatic? Or do they fit in with Sextus’s outlook in PH 1–3, where skeptical arguments are described as leading up to suspension of judgment? Bett (2018, “Introduction”) argues that, with some qualifications, Sextus’ approach is to be explained as follows. Sextus lays out counterarguments based on the assumption that the arguments of the dogmatists have already been formulated. For there to be arguments of equal weight on both sides, only the anti-dogmatic arguments need to be adduced. The intended effect is that jointly, these opposing sets of arguments lead us to suspend judgment. In addition, Bett notes that the remarkable emphasis on counterarguments, non-existence, and uselessness suggests that some of the material in M 1–6 goes back to an earlier phase of Pyrrhonism.

In four of the six fields, namely grammar, rhetoric, music, and astrology, Sextus admits non-technical versions into the skeptic’s life, while subjecting all theoretical claims to skeptical examination. For example, he distinguishes between the ordinary ability to read and write on the one hand and grammar as a technical discipline on the other, or the ability to play a musical instrument on the one hand and music theory on the other (cf. Corti 2015b on why this kind of contrast does not come up in the books on arithmetic and geometry, and Corti 2015c on Sextus’ attack on the Platonic-Pythagorean notion of the Two).

It is remarkable that, qua theoretical field, Sextus examines astrology rather than astronomy. The latter would make for a more typical sequence: apart from the fact that in Sextus, logic is considered part of philosophy rather than a “discipline,” the six fields otherwise correspond to the so-called trivium of grammar, logic, and rhetoric and quadrivium of arithmetic, geometry, astronomy, and music theory. Sextus’ attention to astrology rather than astronomy highlights a deep feature of his philosophy (Corti 2015, Bett 2018). Astronomy, from Sextus’ point of view, is concerned with appearances; and hence there is a sense in which the skeptic does not object to it. Astronomy, then, is the “version” of astrology that skeptics can admit into their adherence to ordinary life (M 5.1–3). Presumably, astronomy is concerned with predicting things like droughts, floods, earthquakes, and plagues based on appearances. Astrology, on the other hand, is concerned with matters of great obscurity.




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