Pyrrhonism Pyrrho Sextus Empiricus
Born1st century BC
EraHellenistic philosophy
RegionWestern philosophy
Main interests
Epistemology, metaphysics, ethics
Notable ideas
The ten modes of Aenesidemus

Aenesidemus (Ancient Greek: Αἰνησίδημος or Αἰνεσίδημος) was a Greek Pyrrhonist philosopher, born in Knossos on the island of Crete. He lived in the 1st century BC, taught in Alexandria and flourished shortly after the life of Cicero. Photius says[1] he was a member of Plato's Academy, but he came to dispute their theories, adopting Pyrrhonism instead. Diogenes Laërtius claims an unbroken lineage of teachers of Pyrrhonism through Aenesidemus, with his teacher being Heraclides and his student being Zeuxippus.[2] However, little is known about several of the names between Timon of Phlius and Aenesidemus, so this lineage is suspect. Whether Aenesidemus re-founded the Pyrrhonist school or merely revitalized it is unknown.


There is no definite evidence about the life of Aenesidemus, but his most important work, the Pyrrhonian Discourses was known to be dedicated to Lucius Aelius Tubero, a friend of Cicero and member of Plato's Academy whom Photius described as a colleague. Based on this information, scholars have assumed that Aenesidemus himself was also a member of the Academy. Furthermore, it has been assumed that he took part under the leadership of Philo of Larissa and probably adopted Pyrrhonism either in reaction to Antiochus of Ascalon introduction of Stoic and Peripatetic dogma into the Academy or Philo's acceptance of provisional beliefs. What little we know of Aenesidemus is by way of Photius (in his Myriobiblion), Sextus Empiricus, and also to a lesser extent by Diogenes Laërtius and Philo of Alexandria.

Pyrrhonian Discourses

His chief work, known in Ancient Greek as Pyrrhoneioi logoi (Πυρρώνειοι λóγοι) and often rendered into English as the Pyrrhonian Discourses or Pyrrhonian Principles, dealt primarily with man's need to suspend judgment due to our epistemological limitations. It was divided into eight books, but it has not survived. We have this summary of its contents from Photius (in his Myriobiblion).

I read Aenesidemus' eight Pyrrhonist Discourses. The overall aim of the book is to establish that there is no firm basis for cognition, either through sense-perception, or indeed through thought. Consequently, he says, neither the Pyrrhonists nor the others know the truth in things; but the philosophers of other persuasions, as well as being ignorant in general, and wearing themselves out uselessly and expending themselves in ceaseless torments, are also ignorant of the very fact that they have cognition of none of the things of which they think that they have gained cognition. But he who philosophizes after the fashion of Pyrrho is happy not only in general but also, and especially, in the wisdom of knowing that he has firm cognition of nothing. And even with regard to what he knows, he has the propriety to assent no more to its affirmation than to its denial. The whole scheme of the book is directed towards the purpose I have mentioned. In writing the discourses Aenesidemus addresses them to Lucius Tubero, one of his colleagues from the Academy, a Roman by birth, with an illustrious ancestry and a distinguished political career. In the first discourse he differentiates between the Pyrrhonists and the Academics in almost precisely the following words. He says that the Academics are doctrinaire: they posit some things with confidence and unambiguously deny others. The Pyrrhonists, on the other hand, are aporetic and free of all doctrine. Not one of them has said either that all things are incognitive, or that they are cognitive, but that they are no more of this kind than of that, or that they are sometimes of this kind, sometimes not, or that for one person they are of this kind, for another person not of this kind, and for another person not even existent at all. Nor do they say that all things in general, or some things, are accessible to us, or not accessible to us, but that they are no more accessible to us than not, or that they are sometimes accessible to us, sometimes not, or that they are accessible to one person but not to another. Nor indeed, do they say there is true or false, convincing or unconvincing, existent or non-existent. But the same thing is, it might be said, no more true than false, convincing than unconvincing, or existent or non-existent; or sometimes the one, sometimes the other; or of such a kind for one person but not for another. For the Pyrrhonist determines absolutely nothing, not even this very claim that nothing is determined. (We put it this way, he says, for lack of a way to express the thought.) But the Academics, he says, especially those from the present-day Academy, are sometimes in agreement with Stoic beliefs, and to tell the truth turn out to be Stoics fighting with Stoics. Moreover, they are doctrinaire about many things. For they introduce virtue and folly, and posit good and bad, truth and falsity, convincing and unconvincing, existent and non-existent. They give firm determinations for many other things too. It is only about the cognitive impression that they express dissent. Thus the followers of Pyrrho, in determining nothing, remain absolutely above reproach, whereas the Academics, he says, incur a scrutiny similar to that faced by the other philosophers. Above all, the Pyrrhonists, by entertaining doubts about every thesis, maintain consistency and do not conflict with themselves, whereas the Academics are unaware that they are conflicting with themselves. For to make unambiguous assertions and denials, at the same time as stating as a generalization that no things are cognitive, introduces an undeniable conflict: how is it possible to recognize that this is true, this false, yet still entertain perplexity and doubt, and not make a clear choice of the one and avoidance of the other? For if it is not known that this is good or bad, or that this is true but that false, and this existent but that non-existent, it must certainly be admitted that each of them is incognitive. But if they receive self-evident cognition by means of sense-perception or thought, we must say that each is cognitive. These similar considerations are set out by Aenesidemus of Aegae at the beginning of his discourses, to indicate the difference between the Pyrrhonists and Academics. He goes on in the same discourse, the first, also to report in summary outline the entire way of life of the Pyrrhonists.

The ten modes of Aenesidemus

Aenesidemus is considered the creator of the ten modes of Aenesidemus (also known as ten tropes of Aenesidemus)—although whether he invented the tropes or just systematized them from prior Pyrrhonist works is unknown. The tropes represent reasons for epoché (suspension of judgment). These are as follows:

  1. Different animals manifest different modes of perception;
  2. Similar differences are seen among individual men;
  3. For the same man, information perceived with the senses is self-contradictory
  4. Furthermore, it varies from time to time with physical changes
  5. In addition, this data differs according to local relations
  6. Objects are known only indirectly through the medium of air, moisture, etc.
  7. These objects are in a condition of perpetual change in colour, temperature, size and motion
  8. All perceptions are relative and interact one upon another
  9. Our impressions become less critical through repetition and custom
  10. All men are brought up with different beliefs, under different laws and social conditions

In other words, Aenesidemus argues that experience varies infinitely under circumstances whose importance to one another cannot be accurately judged by human observers. He therefore rejects any concept of absolute knowledge of reality, since every each person has different perceptions, and they arrange their sense-gathered data in methods peculiar to themselves.[3]

Heraclitean view

Either in the Pyrrhonian Discourses or some other work that did not survive, Aenesidemus assimilated the theories of Heraclitus, as is discussed in the Outlines of Pyrrhonism of Sextus Empiricus. For admitting that contraries co-exist for the perceiving subject, he was able to assert the co-existence of contrary qualities in the same object.[3]

Below, Burnet discusses Sextus Empiricus' reproduction of Aenesidemus account of the theories of Heraclitus. The embedded quote from Ritter and Preller (1898) Historia Philosophiae Graecae (in italics) is Burnet's translation of Ritter and Preller's Greek.

"The locus classicus on this is a passage of Sextus Empiricus, which reproduces the account given by Ainesidemos. It is as follows (Ritter and Preller (1898) Historia Philosophiae Graecae section 41):

"The natural philosopher is of opinion that what surrounds us is rational and endowed with consciousness. According to Herakleitos, when we draw in this divine reason by means of respiration, we become rational. In sleep we forget, but at our waking we become conscious once more. For in sleep, when the openings of the senses dose, the mind which is in us is cut off from contact with that which surrounds us, and only our connexion with it by means of respiration is preserved as a sort of root (from which the rest may spring again); and, when it is thus separated, it loses the power of memory that it had before. When we awake again, however, it looks out through the openings of the senses, as if through windows, and coming together with the surrounding mind, it assumes the power of reason. Just, then, as embers, when they are brought near the fire, change and become red-hot, and go out when they are taken away from it again, so does the portion of the surrounding mind which sojourns in our body become irrational when it is cut off, and so does it become of like nature to the whole when contact is established through the greatest number of openings."

In this passage there is clearly a large admixture of later ideas. In particular, the identification of “ that which surrounds us ” with the air cannot be Herakleitean; for Herakleitos knew nothing of air except as a form of water (§ 27). The reference to the pores or openings of the senses is probably foreign to him also; for the theory of pores is due to Alkmaion (§ 96).

Lastly, the distinction between mind and body is far too sharply drawn. On the other hand, the important role assigned to respiration may very well be Herakleitean; for we have met with it already in Anaximenes. And we can hardly doubt that the striking simile of the embers which glow when brought near the fire is genuine (cf. fr. 77). The true doctrine doubtless was, that sleep was produced by the encroachment of moist, dark exhalations from the water in the body, which cause the fire to burn low. In sleep, we lose contact with the fire in the world which is common to all, and retire to a world of our own (fr. 95). In a soul where the fire and water are evenly balanced, the equilibrium is restored in the morning by an equal advance of the bright exhalation."[4]

"Sextus quotes “Ainesidemos according to Herakleitos.” Natorp holds (Forschungen, p. 78) that Ainesidemos really did combine Herakleiteanism with Scepticism. Diels (Dox. pp. 210, 211), insists that he only gave an account of the theories of Herakleitos."[5]


Unlike other Pyrrhonists who reported that following Pyrrho's prescription contained in the Aristocles passage produced ataraxia, Aenesidemus is reported to have claimed that it produces pleasure (perhaps in addition to, ataraxia).[6]

See also


  1. ^ A. A. Long,D. N. Sedley, The Hellenistic Philosophers, 1987, p 469.
  2. ^ Diogenes Laertius, Lives of Eminent Philosophers "Life of Timon of Phlius" Book IX Chapter 12 Section 116 [1]
  3. ^ a b  One or more of the preceding sentences incorporates text from a publication now in the public domainChisholm, Hugh, ed. (1911). "Aenesidemus". Encyclopædia Britannica. 1 (11th ed.). Cambridge University Press. pp. 257–258. This cites:
  4. ^ Burnet, John (1930). Early Greek Philosophy. 4, 5 & 6 Soho Square, London, W.1: A. & C. Black, Ltd. pp. 152–153.CS1 maint: location (link)
  5. ^ Burnet, John (1930). Early Greek Philosophy. 4, 5 & 6 Soho Square, London, W.1, 1930: A. & C. Black, Ltd. p. 152.CS1 maint: location (link)
  6. ^ Eusebius Praeparatio Evangelica Chapter 18