Context

This guy was living back in the 5th century BCE (pre-Socrates), so we don't know a ton about him. Some evidence suggests that he was exiled from Athens and his works were burned because of his agnostic beliefs…but that's about all we know. Still, a few of his phrases have been passed down and cited by some Big Deal philosophers like Plato.

So what does it mean to be the measure of things? Well, ultimately it's a statement of relativity or subjectivity. Protagoras seems to be saying that each person has his or her own individual truths. Like, to one person, ice cream may taste good, and to another, it might taste bad. 

Actually, scratch that. To one person, ice cream could taste good, and to another, it could taste amazing. It's all relative.

Seems sensical enough, but it works in opposition to what later Greek philosophers like Plato were all about: objectivity. See, Protagoras' own perspective on truth made his statement a weird combination of always true and always not true: "man being the measure of all things is true for me…but it might not be true for you."

People weren't cool with this.

But come on: are philosophers ever cool with anything?

Where you've heard it

You may not have heard this one before, but you've certainly heard "it's all relative."

Same idea.

Pretentious Factor

If you were to drop this quote at a dinner party, would you get an in-unison "awww" or would everyone roll their eyes and never invite you back? Here it is, on a scale of 1-10.

Quoting obscure Ancient Greek philosophers on the subjectivity of truth? If that doesn't sound pretentious to you, then it's not pretentious…to you.