Introduction to Astronomy

they lead and then stop, as that of fire and air upward, and of earth and water downward. The other, however, is circular, which revolves resolutions and alterations from one thing into another, and again from those into this. Therefore, the surrounding world, by its motion, draws this and acts upon the generations and corruptions of things. For generations are in the elements, that is, potentially; but resolution from one into another instantiates the offspring in actuality. For example, in wood, there is smoke in potency, which fire, acting upon the wood, generates in actual fact. Just so, generation and corruption exist in the elements in potency, which the movement of the stars, by altering the elements and resolving them into one another, produces into the thing itself. Moreover, the act of one body of this world upon another is found to be twofold: either by the contact of both, or by some intermediary between them. By contact, as when fire causes combustion in a material; but by another, it is threefold. The first is by volition, as when it moves one thing from another through a medium, touching both extremes at the same time, or intervening between them. The second is by nature, as when fire makes water warm by means of heat. The third is by a certain intrinsic property, as when a magnet stone draws iron through the interval of the air, because the virtue of acting in that way is present in the stone, and the nature of the iron is passive to that action—which nonetheless happens even with another body interposed, such as a copper plate and the like—but it also happens by contact, as when the stone draws the iron and other material often adhering to the iron; and this mode of one thing acting upon another by a certain property of nature is found in many things, both in herbs and in stones, as fire moves colophony a type of resin or oil original: "ebitōz olitē". Therefore, in this way, the celestial essence is seen to act entirely upon the nature of the inferior world. Since such a virtue is not in its own nature, yet the nature of this the inferior world is receptive to such a virtue, from which, by act and passion, the commixture of the world is made, the mother of all generations. Since, therefore, the stars are the first cause of generation, it follows that they obtain the guidance of that same generation. There are indeed some who think that what is from another and what is for the sake of another are the same, and they argue that nothing can be done by another across an interval of space; to whom there are three diversities of such motions. The first is what causes; the second is what happens by the agent; the third is what follows from something else. To do is in two ways: by volition and by nature. By volition, as to go, to stand, to sit. By nature, as for fire to burn. To be done is likewise by volition and necessity: by volition, as to write letters; by necessity, as for material to be burned by fire. But that which is done for the sake of another is different from these. For it is not done by the agent; but by another preceding it, nor does it follow from a certain kinship, like blushing from shame, or pallor from fear. Music produces the modulations of the soul and the consonant motions of the body. To this mode, therefore, when celestial bodies are carried by natural motion over this world, they follow the natural motions of the elements of the inferior world bound to them, producing the generations and corruptions of things. For example: we see the elements scorched by the sun through the quadrant of the first circle, tempered by hot and humid qualities. And thus the earth and trees are clothed with herbs and leaves, adorned with flowers, and the corruption of other things and the generation of others, and in this manner; not from any deliberation of the sun, but by an office divinely enjoined, the same the sun through the circle, and the nature of things is adapted to such motions.