=35.= To the sixth century B.C. belong also the earliest Greek philosophers who are known to us by name. In all of these the early polytheism is either abandoned or becomes so dim in its outlines that the origin and governing force of the universe is sought in quite other directions. The philosophers of Ionia busied themselves with the problem of the elements. THALES of Miletus was a man of many attainments; he had travelled both in Egypt and in Babylon, and was an active political reformer. To him water was the primary substance, from which all others proceeded and to which they returned[19]. ANAXIMANDER of the same town was the first who undertook to give the Greeks a map of the whole known world. To him it seemed that the primary matter could not be the same as any visible substance, but must be a protoplasm of undefined character (ἄπειρον), capable of assuming in turn all shapes[20]. ANAXIMENES (once more of Miletus) assumed air as the first principle, and derived the other elements from it by processes of condensation (πύκνωσις) and rarefaction[21]. But on one point all the Ionian philosophers were agreed: the primary substance was the cause of its own motion; they were ‘hylozoists,’ since they hold that matter (ὕλη) is a living thing (ζῷον). They are from the standpoint of physics ‘monists,’ as opposed to those who hold matter and life, or matter and force, to be two things eternally distinct, and are therefore ‘dualists’ in their theory[22]. [Sidenote: Pythagoras.] =36.= To the same sixth century belong two other notable philosophers. PYTHAGORAS, born in Samos about 575 B.C., and like Thales, one who had travelled widely, left his native land rather than submit to the rule of a tyrant, and founded in Croton in Lower Italy a community half religious and half political, which in its original form was not long-lived. But a widespread tradition remained as to his doctrines, in which the theory of Numbers held a leading position. Pythagoras appears to have been a good mathematician and astronomer, and followers of his school were at an early date led to the doctrines of the rotation of the earth on its axis and the central position of the sun in the planetary system[23]. His name is also connected with the theory of the transmigration of souls, which we may suppose him to have derived ultimately from some Indian source; and to the same country we must look as having suggested to him and his followers the practice of abstaining from animal food[24]. [Sidenote: Xenophanes.]