The philosophy of Aristotle is commonly known to be the reverse of Plato's. Plato started with universals, the very existence of which was a matter of faith, and from these he descended to particulars. Aristotle, on the other hand, argued from particulars to universals, and this inductive method was the true beginning of science. The accumulated knowledge of his age did not furnish him facts enough upon which to build and he had to resort to speculation. It does not detract from the stupendous achievement of this man that the clergy of the Middle Ages, in control of the few isolated centers of learning, looked upon the philosophy of Aristotle as final and considered his works as semi-sacred, and in their immersion in un-reason and unreality, exalted as immutable and infallible the absurdities in the speculations of a mind limited to the knowledge of centuries before theirs. In the attempt to explain plant and animal life, Aristotle formulated the theory that a special form of animating principle was involved. The "elan vital" of Bergson and the theory of Joad are modern reiterations of this conception. Aristotle is not quite consistent when he attempts to give us his theistic beliefs. At times God is, for him, a mysterious spirit that never does anything and has not any desire or will. Elsewhere, he conceives God as pure energy; a prime mover unmoved. Certain modern physicists still cling to this Aristotelian god. This conception of a deity was far from the beliefs of his age, and it is not strange that Aristotle was charged with impiety and with having taught that prayer and sacrifice were of no avail. He fled from Athens and shortly afterwards died in exile. These three supreme Greek thinkers, Socrates, Plato, and Aristotle, have not contributed a single argument for the existence of a supreme being which is now not discredited. Socrates relied on the now outmoded argument from design; and only in a greatly modified form are the arguments of Plato and Aristotle accepted by modern theists. Holding such heretical views in an age when history was a frail fabric of legends, and the scientific explanation of nature in its extreme infancy, what would their views be today? In the consideration of the Greek thinkers of lesser importance one finds that they were continually storming against the religious conceptions of the populace. The philosophers were ever unpopular with the credulous. "Damon and Anaxagoras were banished; Aspasia was impeached for blasphemy and the tears of Pericles alone saved her; Socrates was put to death; Plato was obliged to reserve pure reason for a chosen few, and to adulterate it with revelation for the generality of his disciples; Aristotle fled from Athens for his life, and became the tutor of Alexander." (_Winwood Reade: "The Martyrdom of Man."_)