Democritus of Abdera (between 460 and 360 B.C.), that great investigator of nature and brilliant writer, developed a materialistic doctrine that admits the existence of nothing save atoms and empty space. He conceived the soul to consist of fine, smooth, round atoms, which are also atoms of fire. These atoms are distributed through the whole body, but function differently in different places--in the brain they give us thought, in the heart, anger, and in the liver, desire. Life lasts just so long as we breathe in and breathe out such atoms. The doctrine of Democritus was taken up by Epicurus, who founded his school three hundred years before Christ--a school which lived and prospered for a very long time. Those who are interested in seeing how a materialistic psychology can be carried out in detail by an ingenious mind should read the curious account of the mind presented in his great poem, "On Nature," by the Roman poet Lucretius, an ardent Epicurean, who wrote in the first century B.C. The school which we commonly think of contrasting with the Epicurean, and one which was founded at about the same time, is that of the Stoics. Certainly the Stoics differed in many things from the Epicureans; their view of the world, and of the life of man, was a much nobler one; but they were uncompromising materialists, nevertheless, and identified the soul with the warm breath that animates man. 31. THE MIND AS IMMATERIAL.--It is scarcely too much to say that the Greek philosophy as a whole impresses the modern mind as representing the thought of a people to whom it was not unnatural to think of the mind as being a breath, a fire, a collection of atoms, a something material. To be sure, we cannot accuse those twin stars that must ever remain the glory of literature and science, Plato and Aristotle, of being materialists. Plato (427-347, B.C.) distributes, it is true, the three-fold soul, which he allows man, in various parts of the human body, in a way that at least suggests the Democritean distribution of mind-atoms. The lowest soul is confined beneath the diaphragm; the one next in rank has its seat in the chest; and the highest, the rational soul, is enthroned in the head. However, he has said quite enough about this last to indicate clearly that he conceived it to be free from all taint of materiality.