2.  The Greek philosophy at its height.—­The next succeeding period sees certain classes of questions emerge into prominence which had attracted comparatively little attention from the men of an earlier day.  Democritus of Abdera, to whom reference has been made above, belongs chronologically to this latter period, but his way of thinking makes us class him with the earlier philosophers.  It was characteristic of these latter that they assumed rather naively that man can look upon the world and can know it, and can by thinking about it succeed in giving a reasonable account of it.  That there may be a difference between the world as it really is and the world as it appears to man, and that it may be impossible for man to attain to a knowledge of the absolute truth of things, does not seem to have occurred to them.

The fifth century before Christ was, in Greece, a time of intense intellectual ferment.  One is reminded, in reading of it, of the splendid years of the Renaissance in Italy, of the awakening of the human mind to a vigorous life which cast off the bonds of tradition and insisted upon the right of free and unfettered development.  Athens was the center of this intellectual activity.

In this century arose the Sophists, public teachers who busied themselves with all departments of human knowledge, but seemed to lay no little emphasis upon certain questions that touched very nearly the life of man.  Can man attain to truth at all—­to a truth that is more than a mere truth to him, a seeming truth?  Whence do the laws derive their authority?  Is there such a thing as justice, as right?  It was with such questions as these that the Sophists occupied themselves, and such questions as these have held the attention of mankind ever since.  When they make their appearance in the life of a people or of an individual man, it means that there has been a rebirth, a birth into the life of reflection.

When Socrates, that greatest of teachers, felt called upon to refute the arguments of these men, he met them, so to speak, on their own ground, recognizing that the subjects of which they discoursed were, indeed, matter for scientific investigation.  His attitude seemed to many conservative persons in his day a dangerous one; he was regarded as an innovator; he taught men to think and to raise questions where, before, the traditions of the fathers had seemed a sufficient guide to men’s actions.

And, indeed, he could not do otherwise.  Men had learned to reflect, and there had come into existence at least the beginnings of what we now sometimes rather loosely call the mental and moral sciences.  In the works of Socrates’ disciple Plato (428-347 B.C.) and in those of Plato’s disciple Aristotle (384-322 B.C.), abundant justice is done to these fields of human activity.  These two, the greatest among the Greek philosophers, differ from each other in many things, but it is worthy of remark that they both seem to regard the whole sphere of human knowledge as their province.