AUTHOR’S PREFACE.

...so that they might be able to demonstrate and observe your greatness. Next, in establishing the motions of these, as well as the other five wandering stars Original: "errantium stellarum," the planets Mercury, Venus, Mars, Jupiter, and Saturn., they do not use the same principles and assumptions, nor the same demonstrations of their apparent revolutions and motions. For some use only homocentric circles Circles sharing a single center, usually the Earth; the Aristotelian model., others use eccentrics and epicycles Complex geometric models where circles are offset from the center or move upon other circles; the Ptolemaic model., yet they do not fully achieve what they seek with these. For those who relied on homocentrics, although they demonstrated that several diverse motions could be composed from them, they were unable to establish anything certain from them that clearly corresponded to the phenomena Observed events in the sky.. Those, however, who devised eccentrics, even if they seem for the most part to have accounted for the apparent motions with matching numbers, nevertheless admitted many things in the process that seem to contradict the first principles regarding the uniformity of motion. They were also unable to find or deduce from these the most important thing: the shape of the world and the definite symmetry Proportionality and structural harmony. of its parts.

But it happened to them just as if someone took hands, feet, a head, and other limbs from different places—drawn excellently indeed, but not in relation to a single body—so that they did not match each other at all, and a monster rather than a human was composed from them. Thus in the process of demonstration, which they call a Greek: "methodon" method, they are found to have either omitted something necessary or admitted something foreign and completely irrelevant to the matter. This would least of all have happened to them if they had followed certain, fixed principles. For if the hypotheses they assumed were not fallacious, everything following from them would undoubtedly be verified. Although these things I am saying now are obscure, they will become clearer in their proper place.

When I had turned over in my mind for a long time this uncertainty of the mathematical traditions regarding the calculation of the motions of the world's spheres, I began to be annoyed that no more certain explanation of the movements of the mechanism of the world Original: "machinae mundi," a common metaphor for the universe as a designed structure.—which was built for us by the best and most orderly Craftsman of all—was agreed upon by philosophers, who otherwise examine the most minute things regarding this world so exquisitely. Therefore, I took this task upon myself: to reread the books of all the philosophers I could obtain, to investigate whether anyone had ever thought that there were other motions...