"Although there were many differences among the Sophists in terms of their specific teachings, it is safe to say that there was a common philosophy which many Sophists shared and which permeated their teachings. The most prominent element in this philosophy was skepticism (`a doubting state of mind'). The skepticism of the Sophists took various forms: phenomenalism, the belief that we can only know ideas present in our mind, but not the objects of perception outside our mind (so that it is useless to make a definitive statement about anything outside our own mind); empiricism, the doctrine that experience, particularly of the senses, is our only source of knowledge; and above all, relativism, the theory that truth has no independent absolute existence, but is dependent upon the individual and the particular situation in which one finds oneself.""Although the physis - nomos antithesis was common in the teachings of most Sophists, their views of physis with regard to human nature could differ widely. To some Sophists, the realization that all men have much the same human nature required the abolishment of all artificial distinctions among men, such as Hellene and Barbarian, master and slave. Other Sophists saw human nature as an aggregate of man's animalistic inclinations to aggression and domination by physical strength. Human law (nomos) which restricted those inclinations was seen as an artificial constraint contrary to the natural order of things, created by the weaker members of society. This view was the philosophical basis of the rhetorical argument of "the right of the stronger" ("might makes right") which is used by a number of speakers in Thucydides's History and which you will see advanced by the sophist Thrasymachus in Plato's Republic. The Sophists who advocated this argument saw men in the image of animals in the wild and often recommended the animal world as a model for the human. According to this view, any attempt to constrain the natural human tendency of aggression is not only wrong, but useless. Nature overrides any artificial constraints set up by man. Just as in the animal world, the strong will always be victorious over and dominate the weak. Not all Sophists, however, subscribed to this theory. Protagoras believed that men, left to their own natural savage instincts, would destroy each other. In his view nomos, although only an artificial creation of man, enables men to survive and makes possible civilized communal life."
http://depthome.brooklyn.cuny.edu/class ... phists.htm