"physis" And "nomos"

Sophists were the opponents of the Greek natural philosophy and the innovators of the city-state's traditional concept, including Socrates and Plato's critique, Sophists have been criticized by the public. However, we must focus on the great contribution which Sophists had made in the development of human society. Sophists did not concern the problem of natural world but the political and human affairs, they analysed the essence of politics and justice by making a distinction between "physis" and "nomos". Some of them persisted in the difference between "physis" and "nomos", thus Sophists emphasized human nature as selfishness, which was against the law or the custom's control, Callicles for example; others although approved the difference, they also tried to remit the extreme, they advocated people's selfish natual and recognized the exterior value of "nomos", such as Thrasymachus and Glaucon. By the way, we should pay attention to a special one, he is Protagoras, his argument on "Arete can be taught" and "A human being is the measure" aimed the harmony of "physis" and "nomos". Moreover, their politics involved other problems, such as states,justice and arete. Whatever, justice became the focus discussion of the following philosophers.