Aristotle made many contributions to psychology about the origin and value of the several sensations, about the feelings of pleasure and pain and the desires. He shows his remarkable genius in pointing to the necessity of a unity of consciousness, which he calls the “common-sensibility.” His discussion of the Nous, or reason, is of importance for two reasons: first, because it leads to and illuminates his ethical theory; and second, because it is an example of his deviation from his original conceptual position. The reason, according to his first intention, is the unfolding purpose of the body,――it is the immanent essence of the body. As Aristotle finally left his discussion of the Reason, it is as transcendent as his God, or as any Idea of Plato. The Nous, or Reason, is not a Form of the body, but a Form of the soul. It is purely immaterial, simple, unchangeable, and incapable of suffering. It does not originate with the body as a function. It comes from without as a godlike activity, and will remain after the body passes away. Its fundamental activity is thought, and its object is those ultimate principles of Being which are the ultimate premises of logical thinking. Aristotle’s theory of the Reason is considerably complicated by his division of it into two parts,――the active and the passive Reason. Within itself, the Reason is to be distinguished as Form and Matter. The passive Reason is the Matter for the active Reason, and the active Reason is the Form for the passive Reason. By the passive Reason Aristotle evidently means the individual and developing man. The active Reason can alone persist after death, but whether absorbed in the Deity or not he does not say. Immortality to Aristotle in any case is not a perpetuation of the individuality.