If we turn from etymology to history, and review the labors of the men whom the world has agreed to call philosophers, we are struck by the fact that those who head the list chronologically appear to have been occupied with crude physical speculations, with attempts to guess what the world is made out of, rather than with that somewhat vague something that we call philosophy to-day.
Students of the history of philosophy usually begin their studies with the speculations of the Greek philosopher Thales (b.

624 B.C.).

We are told that he assumed water to be the universal principle out of which all things are made, and that he maintained that "all things are full of gods." We find that Anaximander, the next in the list, assumed as the source out of which all things proceed and that to which they all return "the infinite and indeterminate"; and that Anaximenes, who was perhaps his pupil, took as his principle the all-embracing air.
This trio constitutes the Ionian school of philosophy, the earliest of the Greek schools; and one who reads for the first time the few vague statements which seem to constitute the sum of their contributions to human knowledge is impelled to wonder that so much has been made of the men.
This wonder disappears, however, when one realizes that the appearance of these thinkers was really a momentous thing.

For these men turned their faces away from the poetical and mythologic way of accounting for things, which had obtained up to their time, and set their faces toward Science.

Aristotle shows us how Thales may have been led to the formulation of his main thesis by an observation of the phenomena of nature.