AUTHOR'S PREFACE.

...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; this refers to the five planets known since antiquity: Mercury, Venus, Mars, Jupiter, and Saturn., they use neither the same principles and assumptions, nor the same demonstrations of apparent revolutions and motions. For some use homocentric circles only, others eccentrics and epicycles, by which, however, they do not fully achieve the desired results. For those who relied on homocentrics These are spheres that share a common center, specifically the Earth, a system favored by Aristotle., although they demonstrated that some diverse motions could be composed from them, they could establish nothing certain that would correspond precisely to the phenomena. Those, however, who devised eccentrics A circle whose center is "off-center" from the Earth to account for varying planetary speeds., although they seem for the most part to have resolved the apparent motions with matching numbers, nevertheless admitted many things in the meantime which seem to contradict the first principles regarding the equality of motion. Nor could they find or gather from them the principal thing—that is, the form of the world and the certain symmetry of its parts. But it happened to them just as if someone were to take hands, feet, a head, and other limbs from different places—painted excellently indeed, but not in comparison to a single body—with no part corresponding to the others, so that a monster rather than a human being would be composed from them. Thus, in the process of demonstration, which they call the method original: μέθοδον (methodon), they are found either to have passed over something necessary or to have admitted something alien and hardly pertaining to the matter. This would surely not have happened to them if they had followed certain 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 may be obscure, they will nevertheless become clearer in their proper place.

When I had revolved this uncertainty of mathematical traditions regarding the calculation of the motions of the world's spheres in my mind for a long time, it began to weary me that no more certain reason for the motions of the machine of the world original: machinae mundi; a metaphor suggesting the universe is a divinely designed mechanism.—which was created for our sake by the best and most orderly Maker of all—was clear to the philosophers, who otherwise scrutinize the smallest details with such exquisite care in respect to that universe. Therefore, I took up the task of rereading the books of all the philosophers I could obtain, to search whether anyone had ever been of the opinion that there were other motions...