This important Sophist philosopher (perhaps the chief one in importance) was born in Thrace, in Abdera, during the early 5th century BC.
Apart from philosophy, he was also involved with pedagogy, grammar, rhetoric, and mathematics. He taught widely in various Greek cities, travelling also to Sicily and southern Italy (Magna Graecia).
Athens was, however, his main city where he had close connections with such major figures as Euripidhes, Kallias and Perikles, who assigned him the task of formulating laws for a new colony called Thurii, in southern Italy.
Perikles also put the upbringing of his children in Protagoras' charge, thus demonstrating his high esteem for the teacher. In 410 BC, when he was 70ish, he was convicted by conservative Athenians for atheism and disrespect for the gods, based on the contents of his book entitled, 'Of the gods'.
When his books were burned in the market place, he thought it wise to flee and took a boat for Sicily, but the ship sank and he was drowned before reaching his destination.
Only fragments of his books have survived, though Plato wrote an entire dialogue named for him, which gives some information about his thought. He is known for the following words: 'Man is the measure of all things, of what is, that it is, and of what is not, that it is not.' As a teacher of young people, he taught them prudence and tried to help prepare them for managing households and taking part in civic affairs.