Tetrabiblos (The Quadripartite Book)

Ptolemy says here: that if a man does not assist the operations of the stars which occur in the air—which work with a condition appropriate to the region, the species, the food, and the customs—error will befall him when he wishes to judge. And on account of this he said "the air which surrounds," for what he said before: that the conjunction of the virtues of the stars and their operations are first in the air. And since it is thus manifest, it is fitting for us—if we wish to certify well through this science—that we should always join the operations of the stars with general things, and that in each of them we should look well to the manner; that we should not say of a black man who is the son of a black man that he is white, on account of the fact that the constellation of his nativity demonstrates that he ought to be white; rather, we must say that he is less black than he ought to be. Nor must we say that one who associates with thieves is a man of peace, on account of what is demonstrated in his nativity; but we must say that he will be less evil than other thieves until he leaves their society, and then he will return to his own nature. And thus we must do in all other general and particular things, in laws, and in the accidents of the customs of peoples.

Since, therefore, this is so, it does not mean that because we are sometimes deceived in it, this science is to be entirely disparaged and destroyed. Just as the skill of sailors, who frequently err while navigating, is neither disparaged nor repudiated by us, but rather we ought to remain more attentive and solicitous in it.

After these matters are in this manner, it does not befit us to destroy this whole art on account of some error that sometimes falls therein, just as we ought not to destroy the mastercraft of mariners in directing ships on account of an error that might happen therein, and on account of the fact that it happens many times.

After Ptolemy showed that this art is true, and destroyed the opinions of those contradicting him, and taught us the places in which we must look when we wish to guard ourselves well from error, he said in this place, by way of conclusion: that we ought not to destroy this whole art on account of some small error that sometimes happens therein. And he placed a great distinction between this art and the mastercraft of mariners: that when we look into this art, error happens therein few times, and in the mastercraft of ships, many times. And since it is so, it is fitting that we follow and love this art of judgments more than others, on account of the great profit that lies in it and the small error that happens when we have looked well into it.

For it promises us arduous and estimable things, and let us not doubt that it is possible to attend to what comes from it.

But it is fitting that we seek it and hold it as very noble, because in it are many good and miraculous profits.

These profits which Ptolemy mentions are: such as protection from the harms of enemies, from corrupt air, and from the scarcity of victuals; since we know these things before they happen.

Likewise, it is not fitting that we investigate all things through it, but only those which are investigable. We also say it is necessary that we grasp their materials, nor that we insert what is not suitable.

And let us pursue those things which can be known through these arts. And it is not fitting in the same way to wish to know everything through this art, beyond those things which can be reached by man; and it also befits us to wish for that which is of its pertinence, and that we do not apply to it that which is not of it.

What is said here does not need a gloss.

For just as we do not blame physicians when they seek the occasions of infirmities and the qualities of the infirm, so it ought not to be troublesome to us to investigate materials and regions, foods, and all things that are accidents of the past.

And just as we do not disparage natural philosophers when they inquire by what reason an infirmity happens to the infirm, and the condition pertaining to him, similarly it does not befit us to refuse in this art that we seek about the generation, region, foods, and about all other accidents that occur.

Natural philosophers help themselves much in that which it is fitting for them to know by inquiring about the life that the infirm has used, about the place from where he is, and in all other things which have been said in natural philosophy; and of this no one disparages them; indeed, he praises those who inquire into this more effectively. And since it is so in natural philosophy, which is a present matter, how much more is it so in this art, which is for knowing those things that are future—it is sufficiently clear. Therefore, it is not to be wondered at if one inquires about the generation, and about other things which Ptolemy said.

The third chapter, to demonstrate the utility of this work.

How the prognostications of the stars are grasped, and that it is only those accidents which affect the body of the globe of the earth surrounding [us] and which happen to men on the occasion of these, that becomes known; and that through this, the accidents of men—to their body and soul and their strengths, as well as to their wealth—which have been worked from the first years unto the last, are pertinent; and what are the things that happen extrinsically, which adhere to the aforesaid naturally and inevitably, [this] a certain bond of love desires, which is between the body and the substance, as well as its companion; and as the connection which exists between the soul and its progeny, and the dominion which will happen from them to the rest in the other hours, has been generally proved.

We have generally demonstrated in what manner we shall be able to reach the prognostications of the stars. The sum, indeed, of all that we can know from that is: the accidents that occur in the body that surrounds. And the accidents that occur to men by this reason alone. These accidents which occur to men are those that pertain to the spirit and to the body and to the virtue and works, until the beginning and that which will follow after the works of that thing which was operating in him and in other times; and the things which happen outside those which have a natural and necessary participation with the aforesaid things, such as the participation which is between the body and that which it earns and its companion. And the participation which is between the spirit and the generation and the dominion and the things which a man can have from them according to the times.

Whatever is in this statement are conclusions of those things which he taught us before. We, however, wish to explain each one by itself, so that you may better understand that which he says: in what manner we shall be able to better reach the prognostications through the stars. He means that he has already taught us in what manner we shall be able to know through astronomy things that are future. And that which he said, "The sum of all that we shall be able to know are the accidents that occur in the body that surrounds," he means that the place from where they come are the accidents which happen in the air through the works of the stars. And the accidents which he said occur to men by this reason alone—he means that the things which happen to men on account of the power of the stars do not happen on account of anything else, except on account of the works which the stars perform in the air.