Pyrrho (ca. 360 BC - ca. 270 BC), a Greek philosopher of classical antiquity, is credited as being the first Skeptic philosopher, and the inspiration for the school known as Pyrrhonism founded by Aenesidemus in the 1st century BC.
Pyrrho was from Elis, on the Ionian Sea. Diogenes Laertius, quoting from Apollodorus, says that Pyrrho was at first a painter, and that pictures by him were exhibited in the gymnasium at Elis. Later he was diverted to philosophy by the works of Democritus, and according to Diogenes Laertius became acquainted with the Megarian dialectic through Bryson, pupil of Stilpo.
Pyrrho, along with Anaxarchus, travelled with Alexander the Great on his exploration of the East, and studied under the Gymnosophists in India and the Magi in Persia. This exposure to Eastern philosophy seems to have inspired him to adopt a life of solitude; returning to Elis, he lived in poor circumstances, but was highly honored by the Elians and also by the Athenians, who conferred upon him the rights of citizenship.
Pyrrho wrote nothing. His doctrines were recorded in the satiric writings of his pupil Timon of Phlius (the Sillographer). Unfortunately these works are mostly lost. Today Pyrrho's ideas are known mainly through the book Outlines of Pyrrhonism written by the Greek physician Sextus Empiricus.
The main principle of Pyrrho's thought is expressed by the word acatalepsia, which connotes the ability to withhold assent from doctrines regarding the truth of things in their own nature; against every statement its contradiction may be advanced with equal justification. Secondly, it is necessary in view of this fact to preserve an attitude of intellectual suspense, or, as Timon expressed it, no assertion can be known to be better than another. Thirdly, Pyrrho applied these results to life in general, concluding that, since nothing can be known, the only proper attitude is ataraxia, "freedom from worry". ("By suspending judgment, by confining oneself to phenomena or objects as they appear, and by asserting nothing definite as to how they really are, one can escape the perplexities of life and attain an imperturbable peace of mind.")
The proper course of the sage, said Pyrrho, is to ask himself three questions. Firstly we must ask what things are and how they are constituted. Secondly, we ask how we are related to these things. Thirdly, we ask what ought to be our attitude towards them. Pyrrho's answer was that things are indistinguishable, unmeasurable, undecidable, and no more this than that, or both this and that and neither this nor that. He concluded that human senses neither transmit truths nor lie. Humanity cannot know the inner substance of things, only how things appear.
The impossibility of knowledge, even in regard to our own ignorance or doubt, should induce the wise man to withdraw into himself, avoiding the stress and emotion which belong to the contest of vain imaginings. This theory of the impossibility of knowledge is the first and the most thorough exposition of noncognitivism in the history of thought. Its ethical implications may be compared with the ideal tranquility of the Stoics and the Epicureans.