Xenophanes, who was more of a religious reformer than a philosopher, was so absorbed in the first of these assumptions that he developed it for his purpose in his practical social reformation to the entire neglect of the second assumption. The Eleatics, however, to whose city Xenophanes had come, could not leave his doctrine in its one-sided and undeveloped form. They accepted his teaching of the divine Unchangingness of the universe, but this compelled these profounder thinkers to offer some explanation of the natural processes of change. Change to them cannot really exist. Heracleitus, on the other hand, was impressed with the aspect of life that is expressed in the second assumption of the Milesians――living matter is moving matter. He therefore maintained in direct opposition to the Eleatics, that the changing, living processes of nature alone are real. The two contradictory assumptions that lay so mutually indifferent in the Milesian doctrine thus became the basis of a sharp metaphysical controversy between Heracleitus and the Eleatics. The substance of the world is permanent, change is an illusion, said the Eleatics. The substance of the world changes, permanence is an illusion, said Heracleitus. Either all things are permanent or all things change. These early philosophers had no wealth of empirical knowledge nor of psychological reflection upon which to draw, and it is not strange that they should take extreme positions and be blind to their practical consequences. =1. The Milesian School.= Of all the Greek cities in the sixth century B. C. Miletus was the wealthiest and most prosperous. It was one of the Ionian colonies and was situated on the coast of Asia Minor, and it alone was able to preserve its autonomy as neighbor of the warring eastern empires. Not until the battle of Lade was it captured and destroyed (494 B. C.). From two generations of philosophers history has preserved three names,――Thales, Anaximander, and Anaximenes. The school is called indifferently the Milesian or the Ionic school. The proximity of Miletus to Ephesus, Colophon, and Clazomenæ (as a glance at the map will show) explains the influence of the Milesian school upon the doctrines of Heracleitus, Xenophanes, and Anaxagoras. Undoubtedly the contact of the Milesians with the Orient and Egypt had brought to them knowledge and correct scientific observations of many sorts, especially astronomical. Thales (b. 640 B. C.) was a member of one of the leading families of Miletus, and lived during the flourishing period of the city under the tyranny of Thrasybulus. He is counted among the seven Wise Men, and belonged to the rich commercial class. He probably engaged in commerce and traveled in Egypt. He was versed in the current learning, predicted an eclipse, and was acute in mathematics and physics. Probably he never committed anything to writing. Aristotle’s comments are the only data about him.