=5. Aristotle’s Conception of Nature.= Nature is therefore to Aristotle a far more complex world than Plato had conceived it. Nature has a double character to Aristotle, as his twofold conception of causation shows. Nature is composed of mechanical and teleological causes. Purpose and necessity are the two principles of motion in the world, and in this twofold conception of causation did Aristotle reconcile Plato and Democritus. However much Aristotle concedes to the Democritan idea of mechanical necessity, it is evident that in his conception of nature the principle of teleology predominates over the mechanical. The highest actuality is God, and he is a final or teleological cause; and all results of value in nature come through final causes. Final causes are primary causes; mechanical causes are secondary causes. There would be no motion whatever in the universe but for the highest final cause, God. Yet God is the unmoved mover, and matter cannot move itself. Motion occurs because matter feels the impulse to form itself like God. How different this Aristotelian conception of nature from our modern scientific conception of an impersonal nature under a mechanical causation that is universal! The teleological conception of nature and natural events was very strongly intrenched in the human mind during the Middle Ages, and was not dislodged easily by modern investigation. Nature was a living thing to Aristotle. It was at once intrinsically spontaneous, and self-determined and uniform. Its spontaneity was not that of capricious chance. Its uniformity was that of purpose and end. On the other hand, the Aristotelian conception of nature is not the same as either the Christian doctrine of created nature or Darwin’s theory of ♦evolution. The world of Aristotle had always existed; it is a limited world in space, but not in time. Also the divine reason always existed in it. Yet its evolution is not a progressive climbing sort, like the Darwinian, in which new species evolve. It means only that there is a relationship of rank and value among nature objects. Nature is a unity. Teleological change occurs within it.