An extreme form of skepticism, associated with Pyrrho of Elis (c.365-275 BC) and developed by his followers, notably Aenesidemus (1st century BC) and Sextus Empiricus (2nd century AD). Pyrrhonism’s distinguishing feature lay in its application of scepticism to itself: not only could we not know anything, but we could not even know that we could not know anything.

Unlike the ‘dogmatic’ sceptics of the Academy, therefore (who did claim to know this last fact), Pyrrho advocated complete suspension of judgment and hoped to obtain a tranquil peace of mind thereby – an outlook with echoes in the philosophy of David Hume (1711-1776).

Pyrrho wrote nothing (not surprisingly), but fortunately for our historical knowledge his followers did. ‘Pyrrhonism’ is occasionally used loosely for skepticism in general.

A A Long and D N Sedley, The Hellenistic Philosophers (1987); translations with commentary


Pyrrho of Elis, marble head, Roman copy, Archeological Museum of Corfu

Map of Alexander the Great’s empire and the route he and Pyrrho took to India

Pyrrho of Elis (c. 360 – c. 270 BCE) and his teacher Anaxarchus, both Democritean philosophers, traveled to India with Alexander the Great’s army where Pyrrho was said to have studied with the magi and the gymnosophists,[2] and where he was influenced by Buddhist teachings, most particularly the three marks of existence.[3] After returning to Greece, Pyrrho started a new line of philosophy now known as “Pyrrhonism.” His teachings were recorded by his student Timon of Phlius, most of whose works have been lost.

Pyrrhonism as a school was either revitalized or re-founded by Aenesidemus in the first century BCE.


As with other Hellenistic philosophies such as Stoicism, Peripateticism and Epicureanism, eudaimonia is the Pyrrhonist goal of life. According to the Pyrrhonists, it is one’s opinions about non-evident matters (i.e., dogma) that prevent one from attaining eudaimonia. As with Epicureanism, Pyrrhonism places the attainment of ataraxia (a state of equanimity) as the way to achieve eudaimonia. To bring the mind to ataraxia Pyrrhonism uses epoché (suspension of judgment) regarding all non-evident propositions. Pyrrhonists dispute that the dogmatists – which includes all of Pyrrhonism’s rival philosophies – have found truth regarding non-evident matters. For any non-evident matter, a Pyrrhonist makes arguments for and against such that the matter cannot be concluded, thus suspending belief and thereby inducing ataraxia.

Pyrrhonism is the earliest Western form of philosophical skepticism. In ancient literature Pyrrhonism was commonly referred to as “skepticism,” and Pyrrhonism was often lumped together with the similar philosophy of Academic Skepticism. Correspondingly their practitioners were called “skeptics” and “Academics.”

Although Pyrrhonism’s objective is eudaimonia, it is best known for its epistemological arguments, particularly the problem of the criterion, and for being the first Western school of philosophy to identify the problem of induction and the Münchhausen trilemma.

Pyrrhonists (or Pyrrhonist practice) can be subdivided into those who are ephectic (engaged in suspension of judgment), zetetic (engaged in seeking), or aporetic (engaged in refutation).[4]


Pyrrhonist practice is for the purpose of achieving epoché, i.e., suspension of judgment. The core practice is through setting argument against argument. To aid in this, the Pyrrhonist philosophers Aenesidemus and Agrippa developed sets of stock arguments known as “modes” or “tropes.”

The ten modes 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. Sextus Empiricus attributed them simply to the earlier Pyrrhonists. Diogenes Laeritius attributed them to Aenesidemus. The title of a lost work of Plutarch’s (On Pyrrho’s Ten Modes) appears to attribute the modes to Pyrrho.[5] The tropes represent reasons for epoché (suspension of judgment). These are as follows:

  1. “The same impressions are not produced by the same objects owing to the differences in animals.”[6]
  2. The same impressions are not produced by the same objects owing to the differences among human beings.[7]
  3. The same impressions are not produced by the same objects owing to the differences among the senses.[8]
  4. Owing to the “circumstances, conditions or dispositions,” the same objects appear different. The same temperature, as established by instrument, feels very different after an extended period of cold winter weather (it feels warm) than after mild weather in the autumn (it feels cold). Time appears slow when young and fast as aging proceeds. Honey tastes sweet to most but bitter to someone with jaundice. A person with influenza will feel cold and shiver even though she is hot with a fever.[9]
  5. Based on positions, distances, and locations; for owing to each of these the same objects appear different; for example, the same porch when viewed from one of its corners appears curtailed, but viewed from the middle symmetrical on all sides; and the same ship seems at a distance to be small and stationary, but from close at hand large and in motion ; and the same tower from a distance appears round but from a near point quadrangular.[10]
  6. “We deduce that since no object strikes us entirely by itself, but along with something else, it may perhaps be possible to say what the mixture compounded out of the external object and the thing perceived with it is like, but we would not be able to say what the external object is like by itself.”[11]
  7. “Based, as we said, on the quantity and constitution of the underlying objects, meaning generally by “constitution” the manner of composition.” So, for example, goat horn appears black when intact and appears white when ground up. Snow appears white when frozen and translucent as a liquid.[12]
  8. “Since all things appear relative, we will suspend judgement about what things exist absolutely and really existent.[13] Do things which exist “differentially” as opposed to those things that have a distinct existence of their own, differ from relative things or not? If they do not differ, then they too are relative; but if they differ, then, since everything which differs is relative to something…, things which exist absolutely are relative.”[14]
  9. “Based on constancy or rarity of occurrence.” The sun is more amazing than a comet, but because we see and feel the warmth of the sun daily and the comet rarely, the latter commands our attention.[15]
  10. “There is a Tenth Mode, which is mainly concerned with Ethics, being based on rules of conduct, habits, laws, legendary beliefs, and dogmatic conceptions.”[16]

Superordinate to these ten modes stand three other modes:

  1. that based on the subject who judges (modes 1, 2, 3 & 4).
  2. that based on the object judged (modes 7 & 10).
  3. that based on both subject who judges and object judged (modes 5, 6, 8 & 9)

Superordinate to these three modes is the mode of relation.[17]

The five modes of Agrippa

These “tropes” or “modes” are given by Sextus Empiricus in his Outlines of Pyrrhonism. According to Sextus, they are attributed only “to the more recent skeptics” and it is by Diogenes Laërtius that we attribute them to Agrippa.[18] The five tropes of Agrippa are:

  1. Dissent – The uncertainty demonstrated by the differences of opinions among philosophers and people in general.
  2. Progress ad infinitum – All proof rests on matters themselves in need of proof, and so on to infinity, i.e., the regress argument.
  3. Relation – All things are changed as their relations become changed, or, as we look upon them from different points of view.
  4. Assumption – The truth asserted is based on an unsupported assumption.
  5. Circularity – The truth asserted involves a circularity of proofs.

According to the mode deriving from dispute, we find that undecidable dissension about the matter proposed has come about both in ordinary life and among philosophers. Because of this we are not able to choose or to rule out anything, and we end up with suspension of judgement. In the mode deriving from infinite regress, we say that what is brought forward as a source of conviction for the matter proposed itself needs another such source, which itself needs another, and so ad infinitum, so that we have no point from which to begin to establish anything, and suspension of judgement follows. In the mode deriving from relativity, as we said above, the existing object appears to be such-and-such relative to the subject judging and to the things observed together with it, but we suspend judgement on what it is like in its nature. We have the mode from hypothesis when the Dogmatists, being thrown back ad infinitum, begin from something which they do not establish but claim to assume simply and without proof in virtue of a concession. The reciprocal mode occurs when what ought to be confirmatory of the object under investigation needs to be made convincing by the object under investigation; then, being unable to take either in order to establish the other, we suspend judgement about both.[19]

With reference to these five tropes, that the first and third are a short summary of the earlier Ten Modes of Aenesidemus.[18] The three additional ones show a progress in the Pyrrhonist system, building upon the objections derived from the fallibility of sense and opinion to more abstract and metaphysical grounds.

According to Victor Brochard “the five tropes can be regarded as the most radical and most precise formulation of skepticism that has ever been given. In a sense, they are still irresistible today.”[20]

Criteria of action

Pyrrhonist decision making is made according to what the Pyrrhonists describe as the criteria of action holding to the appearances, without beliefs in accord with the ordinary regimen of life based on:

  1. the guidance of nature, by which we are naturally capable of sensation and thought
  2. the compulsion of the pathé by which hunger drives us to food and thirst makes us drink
  3. the handing down of customs and laws by which we accept that piety in the conduct of life is good and impiety bad
  4. instruction in arts and crafts[21]

Skeptic sayings

The Pyrrhonists devised several sayings (Greek ΦΩΝΩΝ) to help practitioners bring their minds to epoche.[22] Among these are:

  • Not more, nothing more (a saying attributed to Democritus[23])
  • Non-assertion
  • Perhaps, it is possible, maybe
  • I withhold assent
  • I determine nothing (Montaigne created a variant of this as his own personal motto, “Que sçay-je?” – “what do I know?”)
  • Everything is indeterminate
  • Everything is non-apprehensible
  • I do not apprehend
  • To every argument an equal argument is opposed

Similarities with Buddhism

The summary of Pyrrho’s teaching preserved in the “Aristocles passage” shows signs of Buddhist philosophical influence. This text is:

Whoever wants eudaimonia (to live well) must consider these three questions: First, how are pragmata (ethical matters, affairs, topics) by nature? Secondly, what attitude should we adopt towards them? Thirdly, what will be the outcome for those who have this attitude?” Pyrrho’s answer is that “As for pragmata they are all adiaphora (undifferentiated by a logical differentia), astathmēta (unstable, unbalanced, not measurable), and anepikrita (unjudged, unfixed, undecidable). Therefore, neither our sense-perceptions nor our doxai (views, theories, beliefs) tell us the truth or lie; so we certainly should not rely on them. Rather, we should be adoxastous (without views), aklineis (uninclined toward this side or that), and akradantous (unwavering in our refusal to choose), saying about every single one that it no more is than it is not or it both is and is not or it neither is nor is not. The outcome for those who actually adopt this attitude, says Timon, will be first aphasia (speechlessness, non-assertion) and then ataraxia (freedom from disturbance), and Aenesidemus says pleasure.[24]

According to Christopher I. Beckwith’s analysis of the Aristocles Passage, adiaphora (anatta), astathmēta (dukkha), and anepikrita (anicca) are strikingly similar to the Buddhist three marks of existence,[25] indicating that Pyrrho’s teaching is based on Buddhism. Beckwith contends that the 18 months Pyrrho spent in India was long enough to learn a foreign language, and that the key innovative tenets of Pyrrho’s skepticism were only found in Indian philosophy at the time and not in Greece.[26] Other scholars, such as Stephen Batchelor[27] and Charles Goodman[28] question Beckwith’s conclusions about the degree of Buddhist influence on Pyrrho.

Other similarities between Pyrrhonism and Buddhism include a version of the tetralemma among the Pyrrhonist maxims[29] and a parallel with the Buddhist Two Truths Doctrine.[30] In Pyrrhonism the Buddhist concept of “ultimate” (paramārtha) truth corresponds with truth as defined via the criterion of truth, which in Pyrrhonism is seen as undemonstrated, and therefore nothing can be called “true” with respect of it being an account of reality. The Buddhist concept of “conventional” or “provisional” (saṁvṛti) truth corresponds in Pyrrhonism to truth defined via the Pyrrhonist criterion of action, which is used for making decisions about what to do.

Nagarjuna’s Madhyamaka philosophy is particularly similar to Pyrrhonism.[31] According to Thomas McEvilley this is because Nagarjuna was likely influenced by Greek Pyrrhonist texts imported into India

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