Man, they tell us, is a rational animal. Nothing seems more trite to a mind trained in philosophie parlance. Yet the implications of this definition are many and profound. And nowhere do these Implications need to be stressed more than in the field of human knowledge. In explaining how a man knows, it must never be forgotten that we are explaining how a rational animal knows. Too much emphasis placed on either part of the definition results in distorted theory of knowledge, if not in down right nonsense. The investigation ends with a type of knowledge fit only for the angels; or else man is classified as a rather highly organized bit of protoplasm, one step removed from his tree-dwelling ancestors.

Now the rarified atmosphere of the Thomist theory of knowledge with its species, its intellects, agent and possible, might seem to tend toward an excessively rationalistio explanation of knowledge. St. Thomas is, indeed, an intelleotualist; but he does not cut himself off from the true source of cognition sensation, nor does he fail to consider the complete sensitive knowledge which man possesses with brutes. In fact, he make human cognition that of man using his faoulties of intellect and sense. For him, man is one being with one soul in which are radiated all the powers of growth, being, life, sensation, and intellection. Though the operations of the intellect are spiritual and essentially different from those of sense, St. Thomas is careful to show how intellect and sense work together in our human cognition. The continuity, the oneness of the cognitional process, is preserved, and the distinction between faculties, some of which are intrinsically Independent of matter, while others are dependent on matter, is likewise firmly maintained. This cardinal point of Thomist psychology is nowhere better ilustrated than in the Angelic Doctor's teaching on the internal sense in man which is known as the vis cogitative. A careful study of the place of this sense in the Thomist theory of knowlwdge will show the completeness and consistency with which the Angelic Dostor expounds the cognition of a being that is at once animal and rational.