Introduction to Astronomy

...he holds it certain that this species is hot, this cold, this dry or humid, and accommodates it to this or that disease. Just so, the astrologer, from a sensible institution of experiments, is advanced to the natural properties of celestial bodies. He holds the Sun as hot, the Moon as humid, and likewise the power and nature of each star and constellation as certain by the reason of effects. Thus, common crafts are indeed particular. But medicine and astrology seem more universal, in that each embraces the integrity of its own kind; except that we estimate astrology to be as much higher as its matter is more worthy. For medicine is exercised in the natures of the elements and in the alterations of bodies from their composition, state, and accidents; but astrology is entirely consumed in the movement and natures of celestial bodies and their effects through the inferior world. The physician indeed devotes labor to the alterations of the elements. The astrologer follows the movements of the stars, the causes of elemental alteration. Thus, therefore, of all crafts, the science of the stars is found to be as much more noble in kind and higher in dignity as the celestial things excel the terrestrial. Which being so, what should frighten the wise man from either following the movements of the stars or speculating on the effects of the movements, where, with the frequent experiments of predecessors and the acute assertions of philosophers, he holds it certain that the movements of the stars follow the accidents of the world according to the same natures? When he sees generations or corruptions of things impending from the councils of the heavens, why should he, with some reverence retained, not dare to believe what he has as certain, or to enunciate or openly show it? For just as the movements of the elements and the alterations of the seasons and the general accidents of the world openly follow the celestial counsel, so also the movements of individuals of any kind throughout the entire world, between generations and corruptions, increases and detriments, and all alterations, are ordered from the same origin. The ratio of affinity between the whole and the parts holds this. Which all, with the foundation of experiments placed first, the kindred, comparative, and studious investigation has finally attained, so that if ever an error is intertwined with these, it should be argued not as the integrity of the art, but rather the ignorance or negligence of the artist. For it remains for the professor of the art, as often as he undertakes a craft, that he approach entirely instructed in the movements, places, degrees, points, natures, and affections of the stars and constellations, omitting nothing of the natures, qualities, orders, habits, places, times, and aptitude of the stars, proportioned to the habit. To whom, indeed, if these are lacking, it is no wonder if he slips in some part. Therefore, we insinuate where this error can be avoided. For it seems to occur principally for two reasons: one, from a small knowledge of the habit of things in which one must judge what is to be ascribed to things and what to the constellations. Another, from a less sound conception of the celestial counsel, from which frequent mixture and confusion of leadership occurs, so that one cannot lightly choose whom to follow above others. Which being so, neither in this nor in other crafts that pertain to providence, should the part that one has attained be abandoned because one cannot attain everything. For in a moderate...