In the middle of the fifth century B.C.,—when in turn the unrestricted imagination of the Ionian philosophers had failed to explain the riddle of existence on physical grounds, the metaphysical Parmenides had denied the possibility of accurate knowledge, and Zeno, the dialectician of Elea, had reduced himself to dumbness by the conclusion that not only knowledge is impossible but even grammatical predication is unjustifiable, for you cannot say that one thing is another, or like things unlike,—Philosophy fell somewhat into disrepute. A spirit of scepticism spread over the Greek world, and the greatest thinkers, foiled In their attempts to discover the higher truths, turned their attention to the practical side of education. In various cities of Greater Greece there arose men of high intellectual attainment, conveniently classed together under the title of _Sophists_ (educators), who, neglecting abstract questions, undertook to prepare men for the higher walks of civic life by instruction of various kinds. The greatest, of these, Protagoras of Abdera, expressed his contempt for philosophy in the well-known dictum, ‘Man is the measure of all things—of what is, that it is; and of what is not, that it is not.’ He therefore devoted himself to the study of literature, and, in particular, of Homer. He attained great popularity; in the course of long travels throughout the Greek world, he made several visits to Athens, where he knew Pericles. Plato, in the dialogue named after him, gives us some idea of the fascination which his personality exercised over the young men of Athens, and, indeed, ‘Sophistry’ as a whole had a tremendous popularity. All young men of good family and position, who aspired to political life, flocked to hear the lectures of the Sophists. Alcibiades, Critias, and others undoubtedly owed to this movement much of their political ability. The morality of sophistry has been much discussed. The comic poets represent it as the chief instrument for the destruction of the ancient ideals of conduct. Plato, though he recognized its humanistic value and spoke with appreciation of several individual teachers, blamed their teaching as a whole. Certainly the claim of Protagoras, that he could make the worse cause appear the better, laid him particularly open to attack. Protagoras made some elementary studies in grammar, presumably as a basis for logic. His method of teaching was apparently by example. In the dialogue of Plato he gives a demonstration of how a given subject should be discussed: his discourse consists first of a ‘myth,’ then a continuous speech, finally a criticism on a poetical quotation. We may suppose that this is a reasonable imitation of his methods. His pupils committed to memory such speeches, or summaries of them, on various subjects, and were thus moderately well equipped for purposes of general debate.