We must, to be sure, think of pure form at the one end and of pure matter at the other end of our experience. But whatever we actually know consists of pure form and pure matter in correlativity with one another. Whenever we would speak of Socrates, we must not look for some exhaustive description of him by means of reference to an Idea that is “wholly beyond.” Socrates is numerically distinct from Callias because of pure potentiality or matter. Rational explanation must be satisfied with classification.