Anaximenes, born at Miletus 588 B.C., asserted that air was the first principle of the universe; indeed, he held that on it "the very earth floats like a broad leaf." He held that air was infinite in extent; that it touched all things, and was the source of life of all. The human soul was nothing but air, since life consists in inhaling and exhaling, and when this is no longer {218} continued death ensues. Warmth and cold arose from rarefaction and condensation, and probably the origin of the sun and planets was caused by the rarefaction of air; but when air underwent great condensation, snow, water, and hail appeared, and, indeed, with sufficient condensation, the earth itself was formed. It was only a step further to suppose that the infinite air was the source of life, the god of the universe. Somewhat later Diogenes of Apollonia asserted that all things originated from one essence, and that air was the soul of the world, eternal and endowed with consciousness. This was an attempt to explain the development of the universe by a conscious power. It led to the suggestion of psychology, as the mind of man was conscious air. "But that which has knowledge is what men call air; it is it that regulates all and governs all, and hence it is the use of air to pervade all, and to dispose all, and to be in all, for there is nothing that has not part in it." Other philosophers of this school reasoned or speculated upon the probable first causes in the creation. In a similar manner Heraclitus asserted that fire was the first principle, and states as the fundamental maxim of his philosophy that "all is convertible into fire, and fire into all." There was so much confusion in his doctrines as to give him the name of "The Obscure." "The moral system of Heraclitus was based on the physical. He held that heat developed morality, moisture immorality. He accounted for the wickedness of the drunkard by his having a moist soul, and inferred that a warm, dry soul was noblest and best." Anaxagoras taught the mechanical processes of the universe, and advanced many theories of the origin of animal life and of material objects. Anaxagoras was a man of wealth, who devoted all of his time and means to philosophy. He recognized two principles, one material and the other spiritual, but failed to connect the two, and in determining causes he came into open conflict with the religion of the times, and asserted that the "divine miracles" were nothing more than natural {219} causes. He was condemned for his atheism and thrown into prison, but, escaping, he was obliged to end his days in exile.