forms we find other forms similar to higher substances not only in power of motion, but also after a certain sort of a way in power of cognition. . . . Such are the souls of brute animals. Above all these forms we find a form similar to the superior substances, even as regards the kind of cognition which is intelligence, and so is competent for an operation that is accomplished altogether without a bodily organ. This is the intellectual soul" (Contra gentiles, II, 68). But there is no hard and fast line between these gradations of being. "Under each of these orders," adds St. Thomas, "he (the investigator) will find a diversity, accordingly as some are more perfect than others; in such wise that those which are highest in a lower genus are seen to approach a higher genus, and conversely. For instance, animals incapable of locomotion are like plants" (Contra gentiles, III, 97). It was a misapprehension of this truth that led to Leibniz's Law of Continuity and the equally erroneous theory of unity of composition formulated by Geoffrey St. Hilaire.
The soundness and merit of the Angelic Doctor's theory of matter and form are tested not only by its value as affording a norm of scientific classification, but also inasmuch as its application to the development of life is found to square with the researches of Sachs and Haeckel in our own day. The limits of this paper preclude a comparative examination of the results obtained, but the work has been successfully accomplished in Harper's Metaphysics of the School (vol. III, p. 94 et seqq.).
The metaphysical argument demonstrating God's existence is so conclusive that St. Thomas does not hesitate to present it in four different forms. His fourth proof starts from the different degrees of perfection found in the creatures of this visible world. "We discover in our midst," he says, "things more or less good and true and perfect, and so of other qualities. Now, more and less are predicted of things according to their nearness of approach to that which has the quality in the highest degree. . . . Therefore there is something that is best and most true and most perfect and that consequently is being by excellence; for those things that are most true are
