Last updated
Born1st century BC
Era Ancient philosophy
Region Western philosophy
School Pyrrhonism
Main interests
Epistemology, Metaphysics, Ethics
Notable ideas

Aenesidemus (Ancient Greek : Αἰνησίδημος or Ancient Greek : 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 Pyrrhoneia 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.


His chief work, known in Ancient Greek as Pyrrhôneoi 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 Tropes of Aenesidemus

Aenesidemus is considered the creator of the Ten Tropes of Aenesidemus, (also known as the Ten Modes 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
  3. 1 2 Wikisource-logo.svg One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, 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. Eusibius Praeparatio Evangelica Chapter 18

Related Research Articles

Anaxarchus was a Greek philosopher of the school of Democritus. Together with Pyrrho, he accompanied Alexander the Great into Asia. The reports of his philosophical views suggest that he was a forerunner of Pyrrhonism. Aelian writes that he was called Eudaemonicus or "Happy Man"(Ancient Greek: Εὐδαιμονικὸς).

Heraclitus Pre-Socratic Greek philosopher

Heraclitus of Ephesus son of Bloson, was a pre-Socratic Ionian Greek philosopher, and a native of the city of Ephesus, in modern-day Turkey and then part of the Persian Empire.

Zeno of Citium Ancient Greek Stoic philosopher

Zeno of Citium was a Hellenistic philosopher of Phoenician origin from Citium, Cyprus. Zeno was the founder of the Stoic school of philosophy, which he taught in Athens from about 300 BC. Based on the moral ideas of the Cynics, Stoicism laid great emphasis on goodness and peace of mind gained from living a life of Virtue in accordance with Nature. It proved very popular, and flourished as one of the major schools of philosophy from the Hellenistic period through to the Roman era.

Diogenes Laërtius late antique biographer of classical Greek philosophers

Diogenes Laërtius was a biographer of the Greek philosophers. Nothing is definitively known about his life, but his surviving Lives and Opinions of Eminent Philosophers is a principal source for the history of ancient Greek philosophy. His reputation is controversial among scholars because he often repeats information from his sources without critically evaluating it. He also frequently focuses on trivial or insignificant details of his subjects' lives while ignoring important details of their philosophical teachings and he sometimes fails to distinguish between earlier and later teachings of specific philosophical schools. However, unlike many other ancient secondary sources, Diogenes Laërtius generally reports philosophical teachings without attempting to reinterpret or expand on them, which means his accounts are often closer to the primary sources. Due to the loss of so many of the primary sources on which Diogenes relied, his work has become the foremost surviving source on the history of Greek philosophy.

Pyrrho Ancient Greek philosopher

Pyrrho of Elis was a Greek philosopher of Classical antiquity and is credited as being the first Greek skeptic philosopher and founder of Pyrrhonism.

Arcesilaus ancient Greek philosopher

Arcesilaus was a Greek Hellenistic philosopher. He was the founder of Academic Skepticism and what is variously called the Second or Middle or New Academy—the phase of the Academy in which it embraced philosophical skepticism.

Sextus Empiricus ancient Greek philosopher

Sextus Empiricus, was a Pyrrhonist philosopher and a physician. His philosophical works are the most complete surviving account of ancient Greek and Roman Pyrrhonism, and because of the arguments they contain against the other Hellenistic philosophies they are also a major source of information about those philosophies.

Philosophical skepticism is a philosophical school of thought that questions the possibility of certainty in knowledge. Skeptic philosophers from different historical periods adopted different principles and arguments, but their ideology can be generalized as either (1) the denial of possibility of all knowledge or (2) the suspension of judgement due to the inadequacy of evidence.

Xenophanes Presocratic philosopher

Xenophanes of Colophon was a Greek philosopher, theologian, poet, and social and religious critic. Xenophanes is seen as one of the most important presocratic philosophers. Eusebius quoting Aristocles of Messene says that Xenophanes was the founder of a line of philosophy that culminated in Pyrrhonism. This line begins with Xenophenes and goes through Parmenides, Melissus of Samos, Zeno of Elea, Leucippus, Democritus, Protagoras, Nessas of Chios, Metrodorus of Chios, Diogenes of Smyrna, Anaxarchus, and finally Pyrrho. It had also been common since antiquity to see Xenophanes as the teacher of Zeno of Elea, the colleague of Parmenides, and generally associated with the Eleatic school, but common opinion today is likewise that this is false.

Ataraxia is a Greek term first used in Ancient Greek philosophy by Pyrrho and subsequently Epicurus and the Stoics for a lucid state of robust equanimity characterized by ongoing freedom from distress and worry. In non-philosophical usage, the term was used to describe the ideal mental state for soldiers entering battle.

Timon of Phlius Ancient Greek philosopher

Timon of Phlius was a Greek Pyrrhonist philosopher, a pupil of Pyrrho, and a celebrated writer of satirical poems called Silloi (Σίλλοι). He was born in Phlius, moved to Megara, and then he returned home and married. He next went to Elis with his wife, and heard Pyrrho, whose tenets he adopted. He also lived on the Hellespont, and taught at Chalcedon, before moving to Athens, where he lived until his death. His writings were said to have been very numerous. He composed poetry, tragedies, satiric dramas, and comedies, of which very little remains. His most famous composition was his Silloi, a satirical account of famous philosophers, living and dead; a spoudaiogeloion in hexameter verse. The Silloi has not survived intact, but it is mentioned and quoted by several ancient authors. It has been suggested that Pyrrhonism ultimately originated with Timon rather than Pyrrho.

Pyrrhonism is a school of philosophical skepticism founded by Pyrrho in the fourth century BCE. It is best known through the surviving works of Sextus Empiricus, writing in the late second century or early third century CE.

Epoché is an ancient Greek term typically translated as "suspension of judgment" but also as "withholding of assent". The term is used in slightly different ways among the various schools of Hellenistic philosophy.

Aristo of Chios was a Stoic philosopher and colleague of Zeno of Citium. He outlined a system of Stoic philosophy that was, in many ways, closer to earlier Cynic philosophy. He rejected the logical and physical sides of philosophy endorsed by Zeno and emphasized ethics. Although agreeing with Zeno that Virtue was the supreme good, he rejected the idea that morally indifferent things such as health and wealth could be ranked according to whether they are naturally preferred. An important philosopher in his day, his views were eventually marginalized by Zeno's successors.

Agrippa was a Pyrrhonist philosopher who probably lived towards the end of the 1st century CE. He is regarded as the author of "The Five Tropes of Agrippa", which are purported to establish the necessity of suspending judgment (epoché). Agrippa's arguments form the basis of the Münchhausen trilemma.

Münchhausen trilemma A thought experiment used to demonstrate the impossibility of proving any truth

In epistemology, the Münchhausen trilemma is a thought experiment used to demonstrate the impossibility of proving any truth, even in the fields of logic and mathematics. If it is asked how any given proposition is known to be true, proof may be provided. Yet that same question can be asked of the proof, and any subsequent proof. The Münchhausen trilemma is that there are only three options when providing further proof in response to further questioning:

The tetralemma is a figure that features prominently in the logic of India. It states that with reference to any a logical proposition X, there are four possibilities:

Bryson of Achaea was an ancient Greek philosopher.

Benson Mates was an American philosopher, noted for his work in logic, the history of philosophy, and skepticism. Mates studied philosophy and mathematics at the University of Oregon, Cornell University, and the University of California at Berkeley. Some of his teachers included J. Barkley Rosser, Harold Cherniss, and Alfred Tarski. From 1948 until his retirement in 1989, he was a professor of philosophy at Berkeley. He remained Professor Emeritus of philosophy at University of California at Berkeley until his death.

Academic skepticism refers to the skeptical period of ancient Platonism dating from around 266 BC, when Arcesilaus became head of the Platonic Academy, until around 90 BC, when Antiochus of Ascalon rejected skepticism, although individual philosophers, such as Favorinus and his teacher Plutarch continued to defend Academic skepticism after this date. Unlike the existing school of skepticism, the Pyrrhonists, they maintained that knowledge of things is impossible. Ideas or notions are never true; nevertheless, there are degrees of probability, and hence degrees of belief, which allow one to act. The school was characterized by its attacks on the Stoics, particularly the Stoic dogma that convincing impressions led to true knowledge. The most important Academic skeptics were Arcesilaus, Carneades, and Philo of Larissa.