A fellow countryman of Democritus, he recognized the Heraclitean flux and the sensualism of Democritus. Philosophy Protagoras proclaimed that the sensible world is a perpetual metamorphosis. To know the truth, appeal must be made to reflection and reason. But no one knows anything but his own sensations, hence there is no truth for man except in what he perceives, feels, and experiences. The individual is therefore the measure of the true and the good.
Man is the measure of all things.
375 B.C. He was a Rhetorician and orator and wrote a work called On Nature and Non-Being . Gorgias taught that nothing real exists, and even if it did we cannot know it. He asserts that no moral law can be proved, hence man has a perfect right to follow his own notions of good. In the dialogue entitled Gorgias , Plato argues with him that pleasure and worldly goods and the gratification of desires are not happiness. On the Internet Encyclopedia article about Gorgias c. Hippias of Elis Hippias taught science among other things and appears in Plato's Hippias Major , Hippias Minor , and Protagoras .