=1. The Psychology of Aristotle.= As the first experimental psychologist, Aristotle intimately connected his studies in psychology with his studies in biology and medicine. Man is a part of the world of nature, and psychology is in part a comparative study. As we pass upward from the mechanical changes, we find chemical changes of quality, and then changes of organic life. Studying the organic realm, we find ♦organisms to consist of souls of relative ranking. There are vegetative souls, sensitive souls, and rational souls. Plants have vegetative souls with the powers of assimilation and propagation; besides vegetative souls animals have sensitive souls, with the powers of appetition and locomotion; man possesses, besides both these souls, the rational soul. Here is a series of teleological relationships, where the purpose of the organism is explained only by the activity of its soul. The soul builds up its body as a system of organs, and as an organology the theory of Aristotle has great significance. Nature strives ever upward, even in the inorganic processes, through an unbroken series of creations to its highest Form in man. Each step in the upward progress is the realization of an entelechy, or purpose, and constitutes for the moment the goal of the impulse to strive. The whole world is striving to realize the perfect Form. The lower ends, the mechanical and vegetable and appetitive Forms, are not lost but are utilized in the process; for they are the Matter upon which the Forms higher than themselves are built. Every member is both Form and Matter in the whole series. The psychology has therefore two parts: (1) the general theory of animal souls, which possesses rich suggestions; (2) the doctrine of the Nous as the distinctive characteristic of man. These are the empirical and speculative sides to Aristotle’s psychology. Man is an epitome of all the changes in the universe. He has vegetative, appetitive, and rational souls. Yet there is unity in man, for the lower souls are subservient to the reason and exist for it. The appetitive soul is the Form of the vegetative soul, the Matter of the Rational soul, etc. Accordingly, Aristotle defines the soul as the entelechy of the body, because bodily human activity is enlisted in the service of the reason. Reality in man is an unfolding purpose, just as it is in nature. The real self is this unfolding rational self, whose possibility is the body; whose actuality is pure reason. The mind is actualized body, the body is potential mind.