Protagoras, one of the earliest of the Greek Sophists, born at Abdera, and who flourished in 440 B.C., and taught at Athens, from which he was banished as a blasphemer, as having called in question the existence of the gods; he taught that man was the measure of all things, of those that exist, that they are; and of those things that do not exist, that they are not; and that there is nothing absolute, that all is an affair of subjective conception.