Protagoras (c. 490 – c. 420 BC) was a pre-Socratic Greek philosopher born in Abdera, northeast Greece (1). Our main source for him come from Plato (427 – 347 BC) who discusses him in Protagoras and Theaetetus. Diogenes Laertius (180 – 240 AD) and Sextus Empiricus (c. 160 – c. 210) are our other sources although they are centuries removed from the life and times of Protagoras.
From these we learn that Protagoras was a teacher and lecturer who traveled widely. He became the advisor to Pericles, the ruler of the city state of Athens, who instructed Protagoras to write the constitution for the colony of Thurii in 444 BC. Athens was the city in which Protagoras spent most of his time. Protagoras earned his living as a teacher. He taught on the likes of oratory, public speaking, grammar, and poetry, and was also known for the high fees he charged. However, ancient legends accumulated around him which are likely unhistorical. These would include him having studied with Democritus, being jailed for his views, his works and intellectual material burned, and his fleeing from Athens.
Further, much of what we know of him is found within Plato’s writings, and Plato referred to him as a sophist. Sophists, in this context, were traveling intellectuals who were experts in rhetoric. They taught others how to speak in assemblies and in law courts, which were necessary and highly valued skills in Athenian society. As a result they were often private tutors to the youth of the upper classes.
Protagoras is familiar to historians and philosophers for three major themes in his work. One of these is his subjectivist philosophy in which he argued that the interpretation of reality is relative to the individual (his famous statement: “Man is the measure of all things: of the things that are, that they are, of the things that are not, that they are not”). He also claimed that he could make the worse (or weaker) argument appear the better (or stronger), and that one could not tell if the gods existed or not. It seems where the Greek pantheon of gods were concerned Protagoras was agnostic in belief towards them or perhaps even an atheist, which, as some have suggested, might have resulted in the story of the burning of his books by the Athenians.
Through his subjectivist philosophy Protagoras probably did not mean that truth did not exist. Rather, he likely meant that one’s understanding and apprehension of truth is relative to individual perception and what a person holds as true will be true to that individual despite any evidence to the contrary. Therein lies arguably his greatest contribution to western thought, namely, that the world one person sees may be radically different from the world his or her neighbour is experiencing.
According to legend, Protagoras was charged with impiety, a significant offense in Ancient Greece that could result in death, and that while fleeing colony of Sicily he drowned in the sea.