What is the result of such a theory of knowledge? Protagoras expresses it well in his famous words, “Man is the measure of all things.” It is absolute sensationalism. There is no truth except that of the present moment. Each man sees the truth for himself at the moment of his perception. It does not matter if another has a different perception. It does not matter if at the next moment his perception differs. Each perception exists at the moment, is true, and at that moment is the only perception. There are as many truths as there are individuals, as many as there are moments in an individual’s life. Each individual is the measure of the true, the beautiful, and the good; for a thing that is good or true to one man may be harmful or false to another. Metaphysical discussions are vain, for the only reality to prove is the content of the present moment. All causes and ultimate criteria are impossible to be known. =2. The Nihilism of Gorgias.= As the philosophy of Protagoras teaches that everything is equally true, that of Gorgias teaches that everything is equally false. Gorgias declared that Being, knowledge, and the communication of knowledge are impossible. Starting from the dialectic of the Eleatic, Zeno (as Protagoras started from that of Heracleitus), Gorgias maintained: (1) Nothing is; (2) If anything is, it cannot be thought; (3) Even if it can be thought, it cannot be communicated. The knowledge of the thing is different from the thing; the expression of the thought in words is different from the thought itself. =The Ethics of the Sophists.――The Application of their Critical Theory to Political Life.= The ethical-political life was of paramount importance to the Greek. When the later Sophists began to scrutinize it from the point of view of the individual, their skepticism became a direct menace to Greek political institutions. The individual became a law unto himself, and the citizen set himself up as superior to society. Since the time of the Gnomic poets the content of both moral and political laws had become more and more a subject of reflection; and at the time of the Sophists the whole foundation of law was called in question. When the individual man is declared to be the measure of all things, all legal and moral institutions hang in the balance. All rules of conduct and all laws become then artificial and merely conventional products; and just as there is no standard of truth or error in knowledge, so there is no standard of good citizenship or morality. The good man is the prudent man; the good citizen is the successful and powerful man. Might is right.