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Protagoras (c. 490 - 420 B.C.) was a Pre-Socratic Greek philosopher from Thrace in northern Greece, although he made his name as a teacher and advisor in Athens.

Along with his rough contemporary Gorgias, he is considered one of the major figures in the philosophical school of Sophism, and Plato credits him with having invented the role of the professional Sophist or teacher of virtue. He is also sometimes known as the father of Relativism and of Agnosticism.


Protagoras (pronounced pro-TAG-er-as) was born in Abdera, Thrace, in northern Greece. Hints in Plato's dialogue "Protagoras" suggests a date of birth not later than 490 B.C., although exact information is unavailable.

He traveled around Greece for some years earning his living primarily as a teacher and advisor, before settling in Athens. He was well-known there, and became a friend of the prominent Athenian statesman Pericles (c. 495 - 429 B.C.) and other rich and influential Athenians. Pericles apparently invited him to write the constitution for the newly-founded Athenian colony of Thurii in 444 B.C.

Protagoras was probably the first Greek to earn money in higher education and he was notorious for the extremely high fees he charged. His teaching included such general areas as public speaking, criticism of poetry, citizenship and grammar. His teaching methods consisted primarily of lectures, including model orations, analyses of poems, discussions of orthoepeia (the meanings and correct uses of words), and general rules of rhetoric and oratory. His audience consisted mainly of wealthy men from Athens' social and commercial elites.

Many later legends developed around the life of Protagoras (which are probably false), including stories concerning his having studied with Democritus, his trial for impiety and Atheism, the burning of his books, his flight from Athens to Sicily and his death by drowning.

In Plato's dialogue "Meno", Protagoras is said to have died at about the age of 70, after 40 years as a practicing Sophist, which would put his death circa 420 B.C.

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Protagoras apparently wrote many works, the two of which we have definite knowledge being "Aletheia" ("Truth") and "Peri Theon" ("On the Gods"). Unfortunately, none of his works have survived the destruction of the ages. What we know of his works are just a few fragments quoted in the writings of other philosophers, particularly Plato, Aristotle, Diogenes LaŽrtus and Sextus Empiricus.

Although almost a contemporary of Socrates, Protagoras is considered a Pre-Socratic thinker, as he followed more the Ionian tradition of criticism, rather than the more demonstrative method of Socrates and his followers, Plato and Aristotle. However, he did contribute to philosophy a method of finding a better argument by discarding the less viable one (known as "antilogy"). His claim to be able to "make the worse case the better" was a useful oratorical skill in the extremely litigious quasi-democracy of Athens, but it also had the potential for promoting what most Athenians considered injustice or immorality, and led to an increasing distrust of Sophism.

Although quoted out of context in a later work, his most famous saying is originally from his "Truth": "Man is the measure of all things: of things which are, that they are, and of things which are not, that they are not". Another line of Protagoras quoted in Diogenes LaŽrtus' "Lives of Eminent Philosophers" is: "There are two sides to every question". These are both succinct statements of the doctrine of Relativism (that nothing is exclusively good or bad, true or false, and that there is no general or objective truth), and more specifically Moral Relativism. His notion that judgments and knowledge are in some way relative to the person judging or knowing (and indeed that there are as many distinct scales of good and evil as there are individuals in the world), which has come to be known as Ethical Subjectivism, has been very influential and is still widely discussed in contemporary philosophy.

In his lost work "On the Gods", Protagoras wrote: "Concerning the gods, I have no means of knowing whether they exist or not or of what sort they may be, because of the obscurity of the subject, and the brevity of human life". This rather bold admission of Agnosticism, was no doubt quite shocking in his day.

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