The rebellion of Bacon in England was followed by that of Descartes in France, and Leibnitz in Germany. The latter philosopher did much to revive the teachings of Aristotle, likening the series of animals to a chain, each form representing a link. This conception, while good enough in Aristotle’s time, was out of date when revived by Leibnitz, and did much to hamper a true interpretation of the evolutionary sequence. As we shall see more than once in this study, scientific ideas are not like statues or paintings, things of permanent and immutable value. An idea that was good, and valuable, a hundred years ago may be neither today, and its revival would work distinct harm to knowledge. The “faddism” against which enemies of science complain is neither harmful nor iniquitous. An idea should be used to its utmost as long as it represents the height of our knowledge; then, when it has been replaced by new information which is an outgrowth of itself, should be relegated to the museum of scientific antiquities. An ancient, worn-out idea is just as harmful in science as it is in politics; the sooner it is done away with, the better for all concerned. One of the most important, and at the same time, most puzzling, of the German natural philosophers was Emmanuel Kant (1724-1804). When thirty-one years of age Kant published a book entitled, “The General History of Nature and Theory of the Heavens,” in which he attempted to harmonize the mechanical and teleological views of nature. He considered nature as being under the guidance of exclusively natural causes, a very advanced position when compared with the teological conceptions of other Germans. But in his critical work, “The Teological Faculty of Judgment,” published in 1790, he abandoned his progressive views on causation, dividing nature into the ‘inorganic,’ in which natural causes hold good, and the ‘organic,’ in which the teleological principle prevails. He called to the support of this conception the discoveries of the then new science of paleontology, saying that the student of fossils must of necessity admit the existence of a careful, purposive organization throughout both the plant and animal kingdoms. That this assertion was unfounded is shown by the fact that not a few modern paleontologists are strong defenders of rationalism and the mechanistic conception of all life activities. But in spite of the fact that Kant was so awed by the immensity of the problem of organic evolution that he declared it impossible of solution, he nevertheless declared himself in favor of the careful study of all evidence bearing upon it. In a most striking passage, quoted by Schultze and Osborn[4], he says: