The most noted historical writer of the first part of this period was Polybius (about 203-121 B.C.), who wrote a history of the Roman conquests from 264 to 146 B.C. His work, though the larger part of it has reached us in a very mutilated state, is of great worth; for Polybius wrote of matters that had become history in his own day. He had lived to see the larger part of the world he knew absorbed by the ever-growing power of the Imperial City. Plutarch (b. about 40 A.D.), "the prince of ancient biographers," will always live in literature as the author of the _Parallel Lives_, in which, with great wealth of illustrative anecdotes, he compares or contrasts Greek and Roman statesmen and soldiers. CHAPTER XX. GREEK PHILOSOPHY AND SCIENCE. THE SEVEN SAGES; THE FORERUNNERS.--About the sixth century B.C. there lived and taught in different parts of Hellas many philosophers of real or reputed originality and wisdom. Among these were seven men, called the "Seven Sages," who held the place of pre-eminence. [Footnote: As in the case of the Seven Wonders of the World, ancient writers were not always agreed as to what names should be accorded the honor of enrolment in the sacred number. Thales, Solon, Periander, Cleobulus, Chilo, Bias, and Pittacus are, however, usually reckoned as the Seven Wise Men.] To them belongs the distinction of having first aroused the Greek intellect to philosophical thought. The wise sayings--such as "Know thyself" and "Nothing in excess"--attributed to them, are beyond number. The ethical maxims and practical proverbs ascribed to the sages, while, like the so-called proverbs of Solomon, they contain a vast amount of practical wisdom, still do not constitute philosophy proper, which is a systematic search for the reason and causes of things. They form simply the introduction or prelude to Greek philosophy. THE IONIC PHILOSOPHERS.--The first Greek school of philosophy grew up in the cities of Ionia, in Asia Minor, where almost all forms of Hellenic culture seem to have had their beginning. The founder of the system was Thales of Miletus (about 640-550 B.C.), who was followed by Anaximander, Anaximenes, and Heraclitus. One tenet held in common by all these philosophers was that matter and mind are inseparable; or, in other words, that all matter is animate. They never thought of the soul as something distinct and separable from matter as we do. Even the soul in Hades was conceived as having a body in every respect like that the soul possessed in the earthly life, only it was composed of a subtler substance. This conception of matter as being alive will help us to understand Greek mythology, which, it will be remembered, endowed trees, rivers, springs, clouds, the planets, all physical objects indeed, with intelligence and will.