Peritrope (Greek: περιτροπή) is Socrates' argument against Protagoras' view of subjective truth, as presented in Plato's book known as Theaetetus (169–171e).
[2] The term itself came from an ancient Greek word that means "a turning back on one" and likened to the image of a snake devouring its own tail.
[6] This assumption was later refuted due to a mistake on the part of Sextus' interpretation that the Protagorean measure doctrine boiled down to a subjectivist thesis that whatever appearance whatsoever is true.
[7] Well-known attestations of peritrope also include Avicenna and Thomas Aquinas, and in modern times Roger Scruton, Myles Burnyeat, and many others.
Modern philosophers overturning Protagoras' subjective truth include Edmund Husserl and John Anderson.