Bryn Mawr Classical Review

Bryn Mawr Classical Review 2009.10.56

Harald Thorsrud, Ancient Scepticism. Ancient Philosophies.   Stocksfield:  Acumen, 2008.  Pp. xvi, 248.  ISBN 978-1-84465-130-6.  £45.00.  ISBN 978-1-84465-131-3.  £14.99 (pb).  

Reviewed by Diego E. Machuca, Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina) (
Word count: 2791 words

The aim of this work is to offer a comprehensive introduction to the two strands of ancient skepticism -- namely, Pyrrhonian and Academic -- by means of a coherent historical narrative.1 As Thorsrud himself recognizes (pp. x, 16), this is not an easy enterprise, since virtually every part of that narrative could be challenged. Although it is primarily aimed at undergraduate and graduate students, the book is by no means lacking in interest to specialists, since Thorsrud does not sacrifice scholarly analysis and rigor for accessibility. An attractive aspect of his exposition is that he continuously reflects on the sense and soundness of the ancient skeptical stances and explains them both in their own terms and with reference to our current way of seeing things. In other words, he adopts a more philosophic approach by considering the problems addressed by the ancient skeptics or posed by their outlooks, instead of providing an exclusively historical or doxographical presentation of past philosophical views. Thorsrud's interest in ancient skepticism has been motivated by an as yet unfulfilled "desire to find a satisfactory explanation of pervasive disagreement" (p. ix) -- a question that lately has attracted a great deal of attention from epistemologists. He finds that study of the ancient skeptical arguments has helped him think more clearly about the limits of reason, the nature of rational belief and appearances, and the part these play in action, and he expresses the hope that the book will have the same effect on others. Written in a style which is straightforward and readable, this volume is a valuable addition to the ever-growing literature on ancient skepticism.

The introductory chapter presents some of the similarities and differences between Pyrrhonism and Academic skepticism. Thorsrud identifies three similarities. The first is the ability to offer persuasive arguments for and against any given proposition, which leads to suspension of judgment (epochê). The second is the skeptics' characterization of their arguments as ad hominem or dialectical, in response to the charge that skepticism is inconsistent because skeptics claim to know that knowledge is impossible. The third is the skeptics' description of various positive attitudes they take towards appearances, in response to the charge that skepticism is impractical (the famous apraxia objection).

As regards the differences between the two skeptical traditions, Aulus Gellius and Sextus Empiricus claim that the Academic affirms, or claims to apprehend, that things are inapprehensible, something which the Pyrrhonist refrains from doing. Thorsrud joins those who contend that this picture of Academic skepticism is mistaken. Specialists usually claim that Sextus' portrait of some Academic skeptics as what we now call negative (meta)dogmatists -- since they affirm that knowledge of things is impossible -- is biased or partial (see Pyrrôneioi Hypotypôseis [PH] I 3, 226). However, a similar portrait is found in Cicero's Academica I 45 and De Oratore III 67, passages which Thorsrud himself quotes (pp. 12 and 40, respectively). Moreover, two passages from the Academica present Arcesilaus' refusal to make assertions and his withholding of assent as resting on his denial of the possibility of knowledge or apprehension (Acad. I 45, II 59). This shows that the interpretation of Academic skepticism as negative metadogmatism was held by some within the Academy. If this is so, then Sextus' portrait of Academic skepticism is not necessarily biased.

Thorsrud does argue that, according to Sextus, Arcesilaus differs from the Pyrrhonist in that he affirms that suspension of judgment is a good thing and assent a bad thing. Hence, "Sextus thinks Arcesilaus does after all make some assertions about reality" (p. 10, see also pp. 44 and 134). However, in the passage in question (PH I 233) Sextus is only reporting what someone might say about Arcesilaus' outlook, and reading of the entire passage on the relationship between this outlook and Pyrrhonism (PH I 232-234) makes it clear that he does not place trust in the reports that portray Arcesilaus as holding beliefs. Moreover, Sextus recognizes the strong affinity between Arcesilaus' thought and Pyrrhonism, the main reason being his suspending judgment about everything (PH I 232).

Finally, Thorsrud maintains that Aenesidemus (the Academic renegade who in the first century BC started a skeptical movement claiming inspiration from Pyrrho) raised the charge of negative dogmatism mainly or entirely against the Academics of his own day. In Thorsrud's view, Aenesidemus "probably saw the history of the Academy as a gradual decline from the rigorous scepticism of Arcesilaus to the exhausted dogmatic compromises of Philo and Antiochus" (p. 11, cf. 84). If this claim about Aenesidemus' positive appreciation of Arcesilaus' skepticism is correct, then we ought to ask why the former did not turn to the latter as a forerunner rather than to Pyrrho. Perhaps Thorsrud could reply that Arcesilaus was influenced by Pyrrho and Aenesidemus viewed the latter's lifestyle as a model of the skeptical life (see p. 17). Another possible response (suggested to me by a BMCR editor) is that appealing to Pyrrho allowed Aenesidemus to cut himself and his scepticism free from the increasingly dogmatic interpretations of Plato and, hence, of the Academy in his lifetime.

The following six chapters expound the outlooks of each of the ancient skeptics. The first is devoted to Pyrrho and, to a much lesser degree, to his disciple Timon. Thorsrud contends that the reason for Pyrrho's status as the father of Greek skepticism is his novel claim that the state of ataraxia is attained "by means of a firmly unopinionated and indifferent attitude" (p. 18). As expected, most of the chapter is devoted to an analysis of our most important source for Pyrrho's thought, namely, Timon's account of it preserved in Eusebius' Preparation of the Gospel, which in turn quotes Aristocles' On Philosophy. The main controversy about this passage concerns whether Pyrrho adopts a metaphysical or an epistemological position, that is, whether he maintains that things are inherently indeterminate or, rather, that they are indeterminable in the sense that we are cognitively unable to make determinations about them. Although he thinks this controversy cannot be resolved due to the scarcity of our evidence, Thorsrud finds the epistemological reading "slightly more plausible" (p. 25). He is also fully aware that most of our evidence comes from later representatives of the Pyrrhonian tradition who may have projected their own epistemological skepticism onto Pyrrho.

The third chapter of the book is devoted to Arcesilaus, the founder of Academic skepticism. Thorsrud explores the Socratic and Platonic inspiration of Arcesilaus' skepticism as well as Pyrrho's influence. He then examines the debate between Arcesilaus and Zeno over the existence of apprehensive impressions and the former's response to the apraxia objection. Thorsrud rejects the dialectical interpretation of Arcesilaus' practical criterion of "the reasonable", the view that he did not propose this criterion in propria persona, but rather intended to show that, by their own doctrines, the Stoics were committed to epochê and that the reasonable is the only criterion of action available to those who suspend judgment. Regarding Arcesilaus' acceptance of the impossibility of knowledge, Thorsrud contends that he was arguing dialectically against the Stoics, but that given that he succeeded in "refuting all comers, it must have seemed that knowledge is out of our reach" (p. 57). This, however, should be construed as a habitual expectation rather than as a rational judgment: he did not believe that knowledge is impossible although it must have appeared so to him.

The next chapter deals with the skepticism of Carneades. Thorsrud discusses the arguments Carneades used against the theological, ethical, and epistemological theories of his dogmatic rivals in order to show that none of these theories had established what they claim to have established. This failure should lead us to withhold assent, but Carneades distinguishes between two kinds of assent in his reply to the apraxia objection, one of which is acceptable for the skeptic. This distinction, which Cicero presents more precisely as a difference between assenting to appearances and approving those which are persuasive (Acad. II 99, 104), has been construed in two differing ways. According to the first, what Carneades rejects is confident assent to a proposition associated with an allegedly apprehensive appearance, whereas he accepts cautious assent to a proposition associated with a persuasive appearance, i.e., one which is probably true but may be false. On the second interpretation, Carneades rejects assent to the truth of any proposition and hence all belief, whereas he accepts going along with a persuasive appearance which is not taken to be true or even probably true. Thorsrud favors the first, fallibilist reading of the Carneadean distinction, claiming that it avoids the problem of requiring someone "to find something convincing without thereby finding it likely to be true" (p. 80). He also rejects the dialectical interpretation of Carneades' response to the apraxia objection.

A notable feature of the book is that it includes a chapter entirely devoted to Cicero and his own mitigated form of skepticism. The reason is that Cicero's outlook "is worth considering on its own merits" (p. 13), something which Thorsrud can do with authority because he is a specialist in Cicero. He presents the Roman's moderate skepticism as a form of fallibilism. With one possible exception (p. 207, n. 2), Carneades' fallibilism is not associated with his dialectical method and is limited to practical matters. In Cicero, by contrast, the method of arguing for and against any given issue is supposed to provide fallible justification in favor of one of the parties to the dispute, and it extends not only to practical but also to philosophical matters. Thorsrud is aware that his interpretation of Cicero's stance is quite controversial, but he observes that the view it ascribes to Cicero is very similar to the outlook which, according to Charles Brittain,2 Philo of Larissa espoused in the period between his initial radical skepticism and the dogmatism he adopted in his Roman books. Let me finally note that Thorsrud maintains that Arcesilaus' successors were right to mitigate his radical skepticism and that the type of fallibilism adopted by Cicero constituted progress over both the dogmatic positions of Antiochus and the late Philo and the rigorous view of epochê of Arcesilaus and Carneades. I find this somehow surprising, since the reading of the later chapters devoted to Sextus' Pyrrhonian outlook (which does not differ much from Arcesilaus') gives the impression that Thorsrud regards this kind of radical skepticism as intriguing and unassailable.

The sixth chapter, devoted to Aenesidemus, defends the skeptical interpretation of his Pyrrhonism. Thorsrud maintains that Aenesidemus did not adopt a kind of relativism that affirms that knowledge is impossible, but rather a skeptical outlook of the sort Sextus later adopted, according to which the possibility of knowledge cannot be ruled out. Aenesidemus' negative arguments are not expressions of his own view but are meant to counterbalance the opposite arguments, and his relativistic claims actually convey a semantic relativism which presupposes no metaphysical or epistemological commitments. Aenesidemus' skepticism was a synthesis of the Pyrrhonian and the skeptical Academic traditions: he was inspired by Pyrrho's association of epochê with ataraxia and adopted Timon's view of appearances as a practical criterion, but he derived his dialectical method from the practice of the early skeptical Academics. The result was that he used the argumentative practice of the skeptical Academy in view of attaining a tranquil life.

Sextus Empiricus is the subject of the next chapter. Thorsrud discusses the normative and the causal accounts of Pyrrhonism: according to the first, one must or should suspend judgment when one cannot decide among incompatible propositions; according to the second, epochê is something that happens to one when faced with equipollent arguments. The normative account seems to get support from the picture of the skeptic as an open-minded inquirer. Still, Thorsrud favors the causal account because the proto-skeptic's inquiry -- which is aimed at the discovery of the truth and is guided by normative principles -- should be distinguished from the mature skeptic's inquiry -- which is aimed at discovering what arguments and doctrines have been proposed by the dogmatists and is not governed by any such principles. As a matter of habit and disposition, the mature skeptic both continues to examine all the positions in dispute and ends up in a state of epochê after his inquiry. Thorsrud's interpretation here seems questionable. I do agree that the mature skeptic is no longer committed to normative rational principles and that he does not affirm (or deny) that there is a truth to be found, but it does not follow from this that his inquiry is not truth-directed at all. When examining a given conflict among dogmatic theories, he does not merely want to seek out what dogmatists have said on a given issue, but also tries to determine whether the conflict can be resolved in favor of one of the contending parties, that is, whether one of the competing theories is true. Otherwise, would he be a genuinely open-minded investigator? A final, minor remark on this chapter is a caveat concerning the useful chart of Sextus' lost and surviving works found on page 125. Two works which the chart gives as distinct, the Pyrrhonist Discourses -- to which Sextus refers at Adversus Mathematicos (AM) VI 58 and 61 as well as I 282 (missed by Thorsrud) -- and the Skeptical Commentaries -- of which only the five books now called AM VII-XI survive -- are in fact clearly the same work.3

The final two chapters are devoted to examining in more detail some issues relative to the Pyrrhonism defended in Sextus' extant writings. In the first, Thorsrud explores the Pyrrhonian arguments in order to show that they continue to pose a serious challenge to any attempt at rationally justifying our beliefs. He looks in turn at the so-called Five Modes of Agrippa and the arguments Sextus employs in his discussion of the criterion of truth, sign-inference, and proof.

The last chapter analyzes how the Pyrrhonist can practice his skepticism and engage in everyday life without holding beliefs, which is connected with the vexed question of the scope of Pyrrhonian epochê, namely, whether it is unrestricted or is limited to theoretical or philosophical beliefs. These alternatives correspond, respectively, to a phenomenological and an epistemic or judgmental interpretation of the Pyrrhonist's appearances. Although I cannot defend my own view here, let me say that Thorsrud rightly rejects the latter interpretation because "the Pyrrhonist's reliance on appearances in her sceptical practice as well as in ordinary and skillful activities commits her to no beliefs" (p. 174). There are two claims in this chapter with which I must take issue. First, with respect to Sextus' refusal to assimilate Empiricism and Pyrrhonism (PH I 236), Thorsrud claims that "it is more likely that Sextus is only criticizing one version of empiricism" (p. 197). This interpretation, which was defended especially by Michael Frede (whom Thorsrud does not cite), has no evidence in its favor. Indeed, nowhere in his writings does Sextus make any such distinction between two forms of medical Empiricism, one of which would be the sole target of his attack, but rather he ascribes a negative dogmatic position to the Empiricists as a whole.4 Second, Thorsrud claims that Jonathan Barnes takes the terms "rustic" and "urbane" from Galen (p. 213, n. 2), but to the best of my knowledge, only the first of them is taken from Galen, who talks about the agroikopyrrôneioi (De differentia pulsuum VIII 711 K, De praenotione ad Posthumum XIV 628).

The volume also contains a list of the ancient sources used, a chronology of the ancient skeptics, a most useful and well-organized guide to further reading, a list of the references, an index of passages, and a general index. The quality of the production is very good. I noticed only a few errors: on p. 76, "because the rare occurrence" should read "because of the rare occurrence"; on p. 109, "ones feathers" should read "one's feathers"; on page 127, "evidence they can find" should read "evidence he can find"; on p. 149, "is equally wiling" should read "is equally willing"; on p. 211, "both and able and willing" should read "both able and willing"; on p. 216, "Levy" should read "Lévy"; on p. 223, "Romanalcala" should read "Román Alcalá"; and on p. 226, "Riberio" should read "Ribeiro". In addition, on p. 211, n. 10, the reference to Brunschwig's "Once Again on Eusebius on Aristocles on Timon on Pyrrho" should be to his "The hoson epi tô logô Formula in Sextus Empiricus", which however is not listed in the references but in the guide to further reading.

It remains for me only to highly recommend this book to those intending to embark on the systematic study of ancient skepticism or who just want to get an authoritative overview of the field.5


1.   In the United States, the book has been published by the University of California Press.
2.   C. Brittain, Philo of Larissa: The Last of the Academic Sceptics (Oxford University Press, 2001).
3.   On this point, see D. E. Machuca, "Sextus Empiricus: His Outlook, Works, and Legacy", Freiburger Zeitschrift für Philosophie und Theologie 55 (2008), pp. 28-63, at 34.
4.   See especially Frede's "The Ancient Empiricists", in his Essays in Ancient Philosophy (University of Minnesota Press, 1987), pp. 234-260, at 248-249, 251-252, 256-257. For a detailed criticism of Frede's view, see Machuca, "Sextus Empiricus: His Outlook, Works, and Legacy", pp. 49-50.
5.   I am grateful to a BMCR editor for his very useful suggestions, and to Dale Chock for correcting my English.

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