He is known as the first of the Sophists, i.e.
His most important work was 11Epi cuo ew (De natura), of which considerable fragments are extant (chiefly in Simplicius); it is possible that he wrote also Against the Sophists and On the Nature of Man, to which the well-known fragment about the veins would belong; possibly these discussions were subdivisions of his great work.
The Sophists and the Sceptics, Plato and Aristotle, the Stoics and the Epicureans took up the question, and from the time of Locke and Kant it has been prominent in modern philosophy.
A famous problem concerning the cube, namely, to construct a cube of twice the volume of a given cube, was attacked with great vigour by the Pythagoreans, Sophists and Platonists.
The Sophists were the first in Greece to dissolve knowledge into individual and momentary opinion (Protagoras), or dialectically to deny the possibility of knowledge (Gorgias).
