The influence of this school was confirmed by the Aristotelian teaching; if on the one side Aristotle inclined towards the mythical entities of Plato, and the old zoomorphic conception of the world, on the other his theory of perception and of ideas, his amazing observations in physiology and anatomy, and his natural classification of the animal kingdom, induced a positive tendency of thought, an _a posteriori_ method of observation, which awakened the intelligence and predisposed it to a more rational and scientific evolution. His geocentric ideas of cosmogony, his logical forms, the human architecture of the world, his conception of the Being who was the end and cause of motion in all things, were indeed obstinately maintained by the philosophy of Catholics and schoolmen, and served as an obstacle to the real progress of science; but on the other hand, his general method of observing nature, the discoveries which he made, and the tendency of his researches, as well as the importance he assigned to consciousness in the formation of ideas, did much to foster independent inquiry in the history of human thought; and coupled with the earlier mechanical schools, he prepared the way for the evolution of modern science. This is not the place for tracing the simultaneous course of the evolution of the ideal and mechanical schools during the ages which separate us from their origin; and while the influence of the one gradually waned, the other gained strength, although in a sporadic way, first among privileged minds, and then more generally. It necessarily happened that as the evolution of thought went on, impelled by its early tendencies, both mechanical and positive, the ideal system was also modified, and gave place to sounder and truer theories. This great fact, the ultimate evolution of our own time, was effected on the one side by psychological analysis, and on the other by the direct and experimental observation of nature. Setting aside the gradual preparation which led up to this point, we can consider Descartes and Galileo as the representatives of these two great factors; since the one by the analysis of thought, the other by natural experiments, overthrew the mythical ideas, although without being aware that the achievement would produce such grand results.