Tetrabiblos (The Quadripartite Book)

often in predictions which they ought to know through the stars. And if they had known this, they could completely know the particular things due to happen in those matters which it behooves them to know.

¶ For since it is so: if anyone has knowledge of the motions of all the stars, the sun, and the moon, such that he truly recognizes the places and the times in which their figures are formed, and if he does not forget their natures which he has learned through the experiments of many times; even if he does not know their substantial natures, but has recognized the effects which they operate, such as that the sun heats, the moon moistens, and in others similarly, he would be strong in knowing this in a natural way, and would comprehend the mode of signification in the mixing of these through estimation.

¶ And after it is so, what will prevent him who knows the motion of all the stars, and of the sun and the moon, so that nothing is hidden from him in knowing the places and times in which figures occur to them, and he knows the nature of each of them through the opinion of the ancient wise men who were experienced in these things for long times and often—knowing one after another, even if he does not know their substance—yet he knows the virtue of the moon with which it operates, just as the man who knows that the virtue of the sun is heat and the virtue of the moon is moisture; and even if he does not know the virtues of other stars and has the power of knowing these things, yet by himself and through a good sense which he has, he understands the properties of the things which are made through the mixture of this whole, as it indicates the things which have to happen at any time.

¶ The things which were tested and known by proof are those which others have tested, proved, and rectified, and it is fitting that we accept their experience and rectification; and concerning those which others have not been tested for themselves, it is fitting for us to say that they knew them through the doctrine of others. And because the life of man is determined in such a way that it does not suffice to prove all things for himself, it was necessary for him to know those things which others before him have proved, by the demonstration of those who have tested them, so that the fruit and benefit which can be had from thence be not delayed. And because the proposition of man is to know the things which are to be in the future through the operations of the stars, it suffices for a man to know the virtue with which each of them operates and their operations which are made by the mixture of their figures. To know the substances, however, is not for the astrologer, but for the natural philosopher wishing to know the truth.

¶ But what Ptolemy said concerning him who has the power of knowing these things: he wishes to say that he who can know by himself or through others the natural virtues with which the stars perform their operations—which virtues are the four qualities which are made in the air containing us, namely, heat, coldness, humidity, and dryness—can know all other things which are of this science. And yet you will understand when we gloss the words that come after, since it is so. And what he said, that he can know through a good sense what properties the things have which are made through the mixture of this whole, he means to say that a man who will be able to know the compositions of the virtues of the stars can know, through the mixture of the compositions, the virtue which can come from others, because their virtues are mixed together on account of the figures; and he who has known this well, there is nothing that can disturb him when he knows the things which the stars have to operate at any time.

¶ For what, then, could prevent him when he thus recognizes the future changes of the air, so that he predicts it will now be warmer, now more humid? He will also be able to grasp the natural qualities of all men through the qualities of the air, such that he may recognize that the qualities of the body and the soul will turn out in such and such a way, and he may grasp the future events of these occurring at certain hours. Who also, when the ambient air and the nature of the bodies will have acted thus and so, will predict that which is conducive to the health of bodies and their better action. And when the contrary is so, he will judge the contrary.

¶ For judging the proper changes of the air; and he says that it will be warmer or colder. And he will be able to know the proper complexion of any person from the state of the air containing us. And through this, he will know the state of the complexion and of their spirits; and

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he will know the accidents which will happen to him at some times. And when the air which contains us will be of one manner, and the complexion of the body will be of another, it will be tempered and will aid the health of the body toward thickening it; and if it be of another manner, if it will be convenient to the man, [it will be] not tempered.

¶ He means to say that an astrologer is a man who speaks of the virtues of the figures which are made through the motion of the stars and everything else that is said of it; and he has the power of knowing and commanding the particular changes which have to happen in the air. Further, he gives an example, because he will say: "Truly in the future the air will be more humid or drier than it is accustomed to be." And the same he says concerning any day, that on such a day the air will be warmer or colder than what is appropriate to the same time; and because of this, he will be able to know the state of any person, of what complexion he might be, and what his customs will be and what deeds he will do; because when he will have known the virtue of the complexion which will be made in the air through the conjunction of the virtues of the stars at the hour in which the body is formed and established in it, one ought to know well the things which will happen to that body regarding health or infirmity, and that which will happen to the virtues of the spirits of that body and to his customs and deeds; because all these things follow the complexion of the body, as natural philosophers and physicians have tested by right demonstration. Also, he will be able to know that which will happen to any man at any time, because when he will have known the complexion of any man separately and will have known the things which have to happen in the air and which humor will dominate in the brain of this man at such a time, he will know that the customs of that man will be at that time such as are those of a melancholic man. It is fitting, indeed, that you look well into the words of Ptolemy which he said in this place; he says that you should understand them well, and as we teach them, so you will do concerning all the words which he will say, so that you may understand something by yourself.

¶ From the aforesaid, therefore, and from similar things, it is manifest that we can arrive at this work.

¶ For through these things which we have said, and other such things, we will be able to know the things which are of this science, in such a way that we will be able to attain it.

¶ A very good word he said when he says that we will be able to attain it, because through the path by which we know other sciences which are extracted from nature, such as medicine, through this same path we can attain this science; and this is the path which he taught us. But this word which he said is an answer to some saying that this science cannot be attained through nature nor rectification, nor by testing things except through dreams, or through visions, or through prophecies. And Ptolemy by these words thus answers and says: "It may well be true what you say, that this science can be attained through prophecies or visions. We, however, can attain it through the path of nature and of rectification and of testing things." And I say that if you wish to understand well this path which Ptolemy said, look into the book of Galen which he made concerning opinions, and you will understand well that which he said concerning the opinions of the sect of the Empirics. Here, indeed, ends the discussion of what Ptolemy spoke about in this science, that it can be attained. From here on, however, he will speak of the quantity which a man can attain from it, proposing words which are agreeable to this reason.

¶ Who says that this science is to be blamed and put aside, even though they had some frivolous occasions.

¶ They, indeed, who cast out this science, saying that it cannot be attained, give reasons which are not right.

¶ After Ptolemy showed that this science can be attained and taught us the path by which we can attain it, he wishes now to destroy the occasion of those who say that it is not a thing which can be attained in such a way that no reason remains by which one can contradict this science.

¶ The first of which is their great deception, who do not attend to this authority of the science. Since to look into it is a great industry in many ways. And therefore many have opined that it happens by chance, although this science is true.

¶ And we shall know this by these reasons which we shall state. The first reason that they erred in this is that they did not look into this science, nor studied in it as they ought, because it is very great and of many paths; and because of this, some believed that the things which astrologers certify about this art happen by chance and fortune.