Origin of justice. -- Justice (fairness) originates among those who are approximately equally powerful, as Thucydides (in the terrible conversation between the Athenian and Melian ambassadors) comprehended correctly: where there is no clearly recognizable predominance and a fight would mean inconclusive mutual damage, there the idea originates that one might come to an understanding and negotiate one's claims: the initial character of justice is the character of a trade. Each satisfies the other inasmuch as each receives what he esteems more than the other does. One gives another what he wants, so that it becomes his, and in return one receives what one wants. Thus justice is repayment and exchange on the assumption of an approximately equal power position; revenge originally belongs in the domain of justice, being an exchange. Gratitude, too.
Friedrich Nietzsche, Human, All Too Human, #92