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 them are taken from Geometry. Next to this, the science most frequently appealed to is Astronomy. But he also mentions Arithmetic, Optics, Mechanics, Stereometry, Harmonics, and Medicine. Sometimes he refers to questions of Natural History, and at other times to questions of Botany. He even applies his scientific method to Ethics, and shows how we are to obtain a definition of the virtue of magnanimity, by observing the leading characteristics of those who are called magnanimous. The Sciences are not classified here, but a comparative scale of perfection among them is indicated; and those are generally laid down to be the most perfect Sciences which are the most elementary and abstract. But with all this leaning towards an ideal of pure and abstract science, it is remarkable how much the Sciences of Observation are considered in this book, and what an enlightened and modern atmosphere breathes through many parts of it.

In developing his idea of Science, Aristotle takes occasion to controvert several opinions which had found vogue in his day. One of these was that everything in Science could be proved. Some men had a notion that you could go back ad infinitum in proving the principles from which your science was deduced: “This principle was true because of that, and that because of something else, and so on for ever.” Others fancied that by a kind of circular reasoning the propositions of Science might all be made to prove each other. “No,” says Aristotle, “Science must commence from something that is not proved at all.” Science must start from im-mediate principles—i.e., principles