=2. The Relation of Ideas and the World of Nature in the Two Drafts compared.= Plato did not construct his world of Ideas in order to explain the world of physical nature. His original purpose was to find an object for knowledge; and his Ideas were born out of his striving to give a reality to the conceptions of Socrates. In his evaluation of the doctrine of his master he had drawn a distinction between the two worlds, but he had not thought of explaining one by the other. They were related and distinguished, but one threw no light upon the other. In Plato’s first draft of the Ideas he speaks of this relation as _imitation_. The phenomena are an imitation of reality. The Ideas are the originals and physical objects are copies. To state the relation in modern terms, the laws of the growth of a tree are permanent, while the tree changes. The lower world of Becoming has a similarity to the higher world of Being. As the Pythagoreans had conceived things as imitations of numbers, Plato, strongly influenced by the Pythagoreans, thought that concrete things correspond to their class concepts only in a degree. On the one hand, the individual thing partakes of the universal of the Idea, and this is called “participation” in the Idea. On the other hand, the word “presence” describes the way the Idea exists in the thing, which means that the Idea is present in the thing so long as the thing possesses the quality of the Idea. The Ideas are present and then withdraw, and thus the perception changes.