Before culture clash, our social behaviors would have seemed as natural as the seasons — each thought to be controlled by the gods. Nobody, then, would have thought to question whether a behavior was right or wrong, cuz’ matters of right and wrong were already spelled out by god — or nature.
But, some five hundred years before Christ, as cultures near the Mediterranean started to grow and eventually clash with one another, people were finally given reason to question their behaviors.
The Persian King Darius I (550–486 BC), for example, in a rather inspired moment of teaching and, no doubt, to fuck with some Greeks living under his rule at the time, asked the Greeks how much money it would take to convince them to eat the flesh of their fathers when they died. The Greeks, whose custom was to burn their dead, freaked out and said that no amount would convince them. So, King Darius called over the Callatians, whose custom was in fact to eat their dead, and asked them how much money it would take to persuade them to burn their dead. They too freaked out and asked why he would suggest such a thing.
Whatever the effect was on Darius’ subjects, there was one Greek who learned a great deal from these culture clashes. Growing up in a city under the control of Darius’ son Xerxes, Protagoras (c. 490 — c. 420 BC) was a firsthand witness to these clashes — to the competing norms and traditions from those cultures that had been swallowed by the Persian empire — which led him to conclude that our social norms and behaviors are quite different from natural laws.
Social norms, he argued, are created and enforced not by god — or nature — but by each of us.
This had dramatic consequences because it shifted the burden to distinguish between right and wrong from god — or nature — to each individual. Only you, the individual, he claimed, can judge whether a behavior, norm, law, or institution is right or wrong. The burden is yours and yours alone. You can’t shift it to god, nature, history, or even to society because, whatever authority you accept for your actions, it is still you who must accept that authority.