Tetrabiblos (The Quadripartite Book)

and changes by the lunar virtue. And this is a thing which we see with our own eyes; for we see rivers increase and decrease; but [they increase] because the light of the moon increases and decreases. And many trees change their movements according to the rising and setting of the moon, or because it stands in the middle of the sky. And all this is known for certain by physical shepherds, laborers, and sailors; throughout [this book] you will be able to know through the books which the aforementioned [authors] have composed: that vegetables, animals, minerals, and waters are changed in whole or in part according to the change of the light of the moon or according to the figure in which it places itself.

¶ The revolution of the erratic [planets] and fixed stars also produces heats and winds and snows in the air surrounding us in many ways. Wherefore, according to their configuration, alterations occur in the things placed upon the earth.

¶ And the course of the erratic planets and fixed stars acts in the air which surrounds us [to produce] many and diverse effects of heat and cold, of winds, frosts, and snows. And through that change, they change all things which are above the earth by a change similar to it.

¶ Ptolemy taught us that all celestial things are generally of one substance, and that the sun and moon produce many general and particular effects in the things which are among us. And by this, it is fitting that each of the planets and stars should have general and particular effects, just as the sun and moon have. And since they are of one substance, it generally follows that every genus should have species which operate with their substance [to produce] some general effect [that] is in them [as] some virtue. And it is fitting that all other species which are of that genus should have a similar virtue, and that such effects should be produced as is stated in philosophy. And since it is so, it is fitting in every way that the other planets and stars should have a virtue with which they operate in the things that are among us, similarly to how the sun and moon perform that which they do through the change of their virtue [or] they move, i.e., similarly; and they are of one substance, and it is fitting that in other planets and stars [it be the same]: that through their motions and the figures in which they place themselves, they create effects in the things that are among us. But why he said erratic [planets]: he said [it] because they have retrograde motion, direction, altitude and depression, [and] swift and slow course. These are those which we have named before, namely: Saturn, Jupiter, Mars, Venus, and Mercury. And the fixed stars, which are said to be all the other stars which are in the sky, are all fixed because they are always of one mode, namely, one elongated from another. And they are similarly [situated] from the equinox and the zodiac, and through all of them one motion, namely, similarly, reaches [us]: that just as the sun has its own special effect of a different manner than the moon, so each planet and star has its own special and different effect, namely, one from another. And just as the sun and moon operate in things through the change which they make in the air, so the planets and the other stars operate [in] that which they do through the change which they make in the air; and through them, [conditions] are made among us [such as] heat, cold, winds, frosts, snows, and many other things pertaining to the nature of any of them.

¶ And according to their figures toward one another, which they receive from their conjunction and the mixture of their strengths, changes of various kinds occur.

¶ The participation also of the planets and stars in figures, namely, one toward another, makes many and diverse changes when they are conjoined and the virtues descending from them are mixed, namely, one with another.

¶ Since each of the stars has a proper virtue with which it operates according to the change which it makes in the air: it is manifest that when they are conjoined in a figure, their virtues desire to be mixed, their complexions, namely, with another. And from this mixture, another complexion is made, which each one does not have by itself. And through this, it is fitting that they make other great and diverse effects, which each could not produce by itself, and so these effects are many and diverse, but because the mixtures are many and diverse. But when Ptolemy said in the [second] place, he said that that which all the stars operate, they operate through the change which they make in the air, concerning heat, cold, humidity, and dryness. And this is the end of the proof which he gave in the works of the stars. But Ptolemy wishes to explain that which is fitting concerning the things which he said in this proof, so that afterward he will demonstrate [it] inductively.

¶ Besides that the sun in the efficacy of the variations of things ordered in those burning [stars] prevails over the others. The others, truly, sometimes help it and sometimes hinder it, which occurs in the moon more evidently and more frequently, as in conjunction and dichotomy

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and full moon. In other stars, however, it happens in the course of a longer time and by a more hidden signification, according to what is in the hours of their occultation and appearance, and their declination toward any latitude.

¶ Although the virtue of the sun is victorious and dominates in all things existing through order, nevertheless other planets help sometimes and sometimes not, [or] rather they oppose; and this is manifest in the moon and appears more and more frequently, thus in the conjunction of the sun and the moon, and when it is diminished and when it is full. From other planets and stars, however, this happens more from a long time and shows [itself] more hidden, thus in the time in which they appear and in which they are hidden, or in which they decline to some part.

¶ When he said the virtue of the sun is victorious and dominates in things existing through order: it is this which appears in the four seasons of the year, and in the four parts of the day, and in all things which are seen in the works of the sun. And that which he said that other planets and stars help the sun in that which they operate in things which are through order, or arise or decrease in their work; and all [the rest] which he said through this place: he said [it] so that he might demonstrate the effects of the stars and the mixtures which are made through the unions of their virtues, namely, one with another. Similarly, he teaches us through these words that all changes happening in things that are among us occur through the unions of the virtues of the stars and through their mixtures; through which we see in the times that each day [has] different manners, because sometimes the virtue which is the sun's proper [virtue] increases and sometimes it decreases.

¶ And since it is so, let us understand that other planets and stars sometimes help the proper virtue of the sun which are similar to them, [and] sometimes [hinder it] by contraries, [and] by accident [and] by essence; because when some planet or star is of such a nature that it operates an operation similar to that of the sun by accident when it is in a place where its virtue has greater force. And of them, there is another [which is] contrary to the work of the sun through the diminution of its virtue. Similarly by essence or by accident; by essence because its nature is contrary to the nature of the sun, then it opposes the work of the sun, [as] is Saturn; by accident when it is in a place where it can diminish the virtue of the sun. This, indeed, appears in the moon more and more frequently than in any of the others, because it is much around the earth, as we see when it is conjoined with the sun, that when it is halved and when it is full. From other planets and stars, however, this does not appear thus, nor as often, because this does not happen unless when they appear or when they are hidden, or when they decline to some part of the north or south, or [toward] the west or east. And because Ptolemy demonstrates through these words the demonstration of the effects of the planets, and this same [text] shows us the way by which we can know: through complexions, each planet by itself and each star through experience [becomes] such a perfect thing. For when we shall wish to test what the virtue of each of them operates by itself, we test this with respect to the sun and moon, because we already know for certain [that] these two are complexions, because [it is] a thing which visibly appears. And when we shall have known [it] with one, we shall be able to know [it] with others, in this way: by observing when it looks toward itself or is joined, if its virtue increases or decreases; studying in this is not difficult but much [work]. And when we shall have known this, when we shall have inspected, we shall find it to be true; and we shall be certain of that which we shall have found, and we shall have the way to finding that which afterward follows, namely, in this manner: if we shall have found the virtue of some planet that it increases in the heat which the sun makes, and that it decreases in the humidity which the moon makes, and we shall see that the same planet or star decreases in cold and increases in dryness, and we shall test this many times in it, we shall be certain that the same planet or star operates heat and dryness. Through this way, indeed, physicians have found the utility of all mixture and medicine in the preparation of the heat of natural goodness. Now, however, Ptolemy has given in general the rules of the books of this science, as they are placed in them by the ancient wise men, so that they may take them. And if [anyone] shall have wished to test this by himself, they will be able [to do so] through this way.

¶ And since this is the demonstration that this science is true, it could not be firmer.

¶ Since, therefore, the work of the stars is thus, it is necessary that that which they operate through their motions should not only appear in manifest things, but indeed also in the beginning of the operation of seeds and fruits, so that the forms of those modes according to the qualities of the air might be designated in that very hour.

¶ But it is necessary, since this appears from the works of these things in this way, that they do not operate only these things through their motions in the things that we see and feel, [but] they also operate in all living things and those bearing seed and fruit, in the way that they are generated and formed according to the state of the air surrounding them