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Rh without which Aquinas's own unquestionable advance upon Averroës might never, or not so soon, have been made. While, however, Thomas successfully asserted against the Arabians the individuality of the soul, and against the older Aristotelians its substantial unity, there was still another step to be taken before its independence on all sides could be regarded as established, and the ground cleared for the science of Psychology. That step was taken by Descartes, in whom mankind may be said to have come to a consciousness of itself. His "Cogito, ergo sum" (I think; therefore I am), was not logical, but genetic. The force of the ergo (therefore), as Ferrier long ago pointed out, lay in the fact that the existence of Descartes as a self-conscious being—sum (I am)—was resultant upon the process described by the word cogito (I think)—the turning of the light of self-consciousness upon the thinking principle itself. We have but extended Ferrier's interpretation from the development of self-consciousness in the individual to the metaphysical evolution of the ego (me) in human history. Not till this had been accomplished, and the Mind made a separate individual existence as against God and Nature, was any independent science of Psychology possible. Observations and reasonings on Man, as on the Deity and the Creation, formed part of the "undifferentiated" mass of speculation on things in general called Cosmology or Theology, and latterly, in a mutilated condition, Metaphysics. Any mediæval cyclopædia will furnish illustrations.

Thomas Aquinas, a faithful representative of the frightened orthodoxy of the Middle Ages, unsuspectingly follows the course of Creation, well known to have happened as laid down in the Book of Genesis. After forty-four Quæstiones (Questions) on God (under whom he discusses the nature of ideas and the metaphysics of truth) and the Trinity, and thirty on the Angels, the Devils (here arises, naturally, a discussion on the nature of evil), and the seven days of creation and rest, Thomas arrives, by an obvious logical sequence, at the psychology of man. One quæstio (question) settles the essence of the soul, another the union of soul and body; three exhaust the powers of mind in general and special, and the intellectual powers; four expound appetite, sensuality, the will, and free-will; and, having in seven more disposed of the remaining faculties of the soul, including such small subjects as "the mode and order of intellection," Thomas is prepared to deal with the production of man's body, and then evidently with the production of woman's body. A witty journalist is reported to have said of an eminent living thinker, "God made the world in six days, and So-and-so wrote it down on the seventh;" but the entire Synthetic Philosophy might fall out of a corner of the