Protagoras
Overview
 
Protagoras (ca. 490 BC – 420 BC) was a pre-Socratic
Pre-Socratic philosophy
Pre-Socratic philosophy is Greek philosophy before Socrates . In Classical antiquity, the Presocratic philosophers were called physiologoi...

 Greek philosopher and is numbered as one of the sophists by Plato
Plato
Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

. In his dialogue Protagoras
Protagoras (dialogue)
Protagoras is a dialogue of Plato. The traditional subtitle is "or the Sophists, probative". The main argument is between the elderly Protagoras, a celebrated sophist, and Socrates...

, Plato credits him with having invented the role of the professional sophist or teacher of virtue. He is also believed to have created a major controversy during ancient times through his statement that man is the measure of all things. This idea was very revolutionary for the time and contrasting to other philosophical doctrines that claimed the universe was based on something objective, outside the human influence.
Protagoras was born in Abdera, Thrace
Abdera, Thrace
Abdera was a city-state on the coast of Thrace 17 km east-northeast of the mouth of the Nestos, and almost opposite Thasos. The site now lies in the Xanthi peripheral unit of modern Greece. The municipality of Abdera, or Ávdira , has 18,573 inhabitants...

, in Ancient Greece.
Quotations

Man is the measure of all things: of things which are, that they are, and of things which are not, that they are not.

As quoted in Theaetetus by Plato section 152a

There are two sides to every question.

As quoted in Lives of Eminent Philosophers, by Diogenes Laertius|Diogenes Laertius, Book IX, Sec. 51

The Athenians are right to accept advice from anyone, since it is incumbent on everyone to share in that sort of excellence, or else there can be no city at all.

As quoted in Protagoras by Plato

When it comes to consideration of how to do well in running the city, which must proceed entirely through justice and soundness of mind.

As quoted in Protagoras by Plato

You, Socrates, began by saying that virtue can't be taught, and now you are insisting on the opposite, trying to show that all things are knowledge, justice, soundness of mind, even courage, from which it would follow that virtue most certainly can be taught.

As quoted in Protagoras by Plato

 
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