No that isn’t a spelling mistake, I do mean the name Protagoras (c. 490 – c. 420 BC)! He was a Greek philosopher and named by Plato to be a ‘Sophist’ (a specific kind of teacher from the time, who specialised in philosophy and rhetoric). He’s arguably most famous for his saying:
“Of all things the measure is Man, of the things that are, that they are, and of the things that are not, that they are not”
This is more commonly shortened to ‘Man is the Measure of All Things’, which is often interpreted to mean that values come from within each individual human being (rather than a god or deity). ‘What you feel to be true is true for you, what I feel to be true is true for me, and there is no reason they should be the same.’
This view was controversial at the time, as Athenians held piety of high importance. As a result Protagoras drowned in the sea while fleeing for safety, after being charged with impiety!
Sources: Wikipedia (http://www.wikipedia.com) | Listverse (http://listverse.com/2012/06/26/top-10-pre-socratic-philosophers) | Ancient History Encyclopaedia (http://www.ancient.eu/article/61)