Ten Treatises on Astronomy (Book of Astronomy)

The mastery original: "magisterium" of the stars and their works are the most noble and exceed all other masteries and operations. Indeed, a perfect cause leads to a perfect effect. For the physician involves himself with lower, corruptible bodies that are subject to alteration and the like. The astrologer, however, involves himself with the operations of the super-celestial bodies, which are neither corrupted nor altered. Indeed, these heavenly bodies act upon the lower, corruptible bodies with which the physician occupies himself. Within the heavenly bodies themselves, there is nothing corporeal that acts or is acted upon, nor will they be acted upon until that day which God willed, of which it is said that neither the angels nor the Son know, but the Father alone, etc. This is because all lower bodies—that is, the elemental things—consist of the four elements Earth, Water, Air, and Fire, all of which are corruptible; and no one doubts that this is true. The celestial bodies, however, consist of another essence which is different from those four elements: namely, the fifth essence quintessence; a refined substance believed by medieval philosophers to compose the heavens, making them eternal and unchanging, which is incorruptible and impassible. For if it were made of these four elements, it would suffer and be subject to the alterations of growth and decay, just as happens to these lower, corruptible things. And for this reason, it is said that the super-celestial bodies are made of a fifth matter or fifth essence. These bodies move with a natural motion, as it has seemed to some; and to others, it has seemed that they move with a voluntary motion. They are moveable but not changeable by any altering motion, and they are bright, round, and spherical—which is the most noble form above all other forms. The mutations, alterations, and conversions that occur arise from the motions of the stars surrounding us, which move and affect the elements until their ends, as has been said, in a restless revolution that does not finish and shall not finish except as previously stated. It has been said philosophically that terrestrial motion is joined to the celestial world, though this must be understood metaphorically and not absolutely; and because of this, mutations, alterations, and corruptions occur in this corruptible world. Since the solidity of the celestial world reaches all the way to the elements, it surrounds the fire, and the fire surrounds the air, and the air the water and the visible earth, and the water the earth; and from this comes the corruption of the elements and of individual elemental things.

Chapter Two: Showing that the stars impress upon lower bodies and that the changes which occur in this world happen by their motions.

Concerning the four elements

Principles should not be proven but assumed, since all principles are reduced to the one principle that is before all things besides itself. For I do not believe anyone doubts that the motion of the heaven, surrounding the elements, changes the fire and the air; and these in turn change the other elements, namely water and earth, and all living creatures, plants, and other things that have their existence beneath the lunar circle. All these things exist within them and undergo mutation or alteration. For the sun and the air work upon all earthly individuals and the parts of individuals; since no alteration happens to the earth except from the mutation of the sun through the signs—that is, the four seasons of the year, which are: Spring, Summer, Autumn, and Winter. This appears manifest in the fruits and leaves of trees, and also in animals which, at certain times of the year, join together and are moved to the generation of individuals of their species. This is seen especially in Spring more than in other times of the year, as the fig tree and the shoots of plants demonstrate when their fruit is present. And we also see, from the daily rotation, the earth grow warm, cool down, dry out, and become moist. We likewise see at certain times of the year the flooding of waters and other mutations that occur because of the circular revolution of the driving heaven; and from this, alterations happen to all things placed on the earth, and especially in

the waxing and waning of the light of the moon; because the moon is closer to the earth than the other stars, its impressions are more strongly felt. Similarly, the heat of the sun is felt more than the others, although perhaps other planets sometimes increase its efficacy and sometimes diminish it according to their nature, as they are applied to the sun or the sun to them. The impressions of the other stars are not felt as readily, but their effects appear over longer periods of time. The effects of the sun also appear manifest in the leaves, flowers, and fruits of trees and herbs, and even more clearly in those things which are sown and planted than in others. For although the stars work, their effects cannot appear as clearly to the common people; they are, however, known by those skilled in the sciences. The other stars, along with the planets, act upon lower things by means of motion and generation.

Chapter Three: How one arrives at the science of astrological judgments, and what can be excused.

From Astrology one knows the past, present, and future.

Not only the thought of present things, but the remembrance of the past and the foresight of the future; namely of species and individuals, and even of the two parts of the world. For through the subjects of the sciences, their effects and their utility are known; although perhaps certain envious people might say that astronomy astrology is nothing. It is certain that it is one of the four mathematical sciences the Quadrivium: Arithmetic, Geometry, Music, and Astronomy, and indeed the most noble. And if it is the most noble, it has the most noble effects and its utility is greater, as will be said in its proper place in what follows; for the subjects of the other mathematical sciences are beneath the subject of astronomy. The subject of Astrology is the quality of motion of any celestial body. For the subject of arithmetic is number; of geometry, measure; of music, harmony (as is said elsewhere); these are noble by reason of demonstration. The subject of astrology, however, is the quality of the motion of the super-celestial bodies. The astrologer knows what kind of motion every super-celestial body has; if he knows the qualities of the motions, he knows what kind of impressions they impress and what their significations are. Everything that happens on earth according to the natural order, and in the other elements, happens from the motions of the super-celestial bodies; this seems doubtful to no one, unless perhaps to someone who is neither wise nor a simpleton i.e., someone willfully ignorant; and these things are known by the astrologer for the reason aforesaid. Therefore, all things that happen at present, and which have been until now, and which happen in the future, can be known by the astrologer since he knows the qualities of the motions which were, which are, and which will be afterward: in what times they will be and what will fall out from them or because of them.

Chapter Four: Against those who say that the science of the stars cannot be known by anyone.

Since they have said this science is to be despised, even though their reasons are frivolous, they have nevertheless found some occasions to reject it. The first of these is: that the science of the stars cannot be known in its entirety, saying that the Empyrean heaven is entirely stars and that it shines and impresses just as the other stars do—as certain foolish, truncated people say—and the astrologer makes no mention of it; therefore, it seems that the science of the stars is not known fully. To whom it seems to me that a brief answer can be given in one way: namely, that they do not prove it to be so, and thus their contradiction is void. If, however, I wished to consider plainly that it were so, it seems that they could be answered thus: namely, that although their objections have the appearance of truth, they do not have the reality. If the ninth heaven is entirely a star, as they say, it has no motion, as has been said. Furthermore, all its parts are equally powerful, nor can one part do more or less than another; and thus it works equally and everywhere with all its parts, influencing or impressing, because all its parts and each one are equal and equally powerful, nor do they differ in light, number, or any other virtue; nor is it moved from place to place, nor toward a place. The parts...