Peritrope

The Peritrope is Socrates' argument against Protagoras' view of relative truth, as presented in Plato's book known as Theatetus (169–171e). The name comes from the ancient Greek for "turning around". Sextus Empiricus is thought to have given the name in a comment on the passage. The name has been in continuous use ever since, as Socrates' argument provides the foundation for classical propositional logic and hence much of traditional western philosophy (or analytic philosophy). Well-known attestations of Peritrope include Avicenna and Thomas Aquinas, and in modern times Myles Burnyeat and many others. The word is occasionally used to describe argument forms similar in nature to that of Socrates' overturning of Protagoras.