Tetrabiblos (The Quadripartite Book)

Paly spoke.

Ptolemy gives in this chapter a demonstration of what can be attained in this art—that it is customary in it—and he shows that it is that which can be attained; and with this he demonstrates that the art is true. And since it is so, how could anyone opine that it was not a tested thing? For this art is true, but no one has spoken in it with reason; rather, if you examine the words which they said, you will find them very far removed from the truth, and you will seek [to show] that the words of Ptolemy cannot be falsified.

That there exists in the aether something which, reaching down to terrestrial things, is said to change them—rather, it compels these same things to undergo natural mutability anew from the two primary materials placed beneath the lunar circle, which are fire and air, which the motion of the aether surrounds and changes, and in them the rest, namely water and earth, and it surrounds their individual vegetables, and by its mutations changes them—we believe there is no doubt.

The word spoken regarding the noble substance which has a known virtue, and that this virtue descends to all things that are above the earth, moving and changing them, and that these also receive motion and mutation from the two elements which are below the sphere of the moon—and these are fire and air, which are surrounded and receive motion and mutation from the motions of the noble body—and they themselves likewise provide and change by their motion other things which are in them, just as are the earth, water, and all things that are in them, of vegetables and animals: the word is true and a certain thing and manifest to all.

Ptolemy proves this by a certain and direct proof of judgment, which is called experience in this manner: because laborers know by the course of the planets the times that are coming for planting trees, for sowing, for causing beasts to breed, and those who are wiser in the labors of the earth, just as those who made books on agriculture, know from the stars that which will happen to any tree in the hour in which it is planted, and that which will happen to them when they will bear fruit.

The celestial bodies are a noble substance, which generally are all one in kind, and they are the nature and substance of another, as also are other things which are below the sphere of the moon, because that is a firm and durable substance, always of one mode, while the substance of things which are among us is convertible and of many mutations. And it is manifest that the virtue coming to us from the superior bodies performs and makes mutations in the inferior bodies. For all who wish to examine in a certain way will see that sometimes the air, having been chilled, becomes hot and dry, and moist; it changes all things existing upon the earth because of this, just as [it does] water and vegetables and animals. And Ptolemy proves this by a certain and direct proof of judgment, which is called experience in this manner: because laborers know by the course of the planets the times that are coming for planting trees, for sowing, for causing beasts to breed, and those who are wiser in the labors of the earth, just as those who made books on agriculture, know from the stars that which will happen to any tree in the hour in which it is planted, and that which will happen to them when they will bear fruit. Sailors, however, know from the stars when they ought to direct their ships, and those who are wiser understand the things which happen in the sea. And those who are dwelling on the banks of the sea know from the stars how the sea grows and decreases; in the same way, rivers and springs change. Physicians also know from the stars and planets which air gives health and infirmity. And he who knows more and examines great things, [is able] to know the particular things pertaining to his mystery. Just as Hippocrates, who said: if the infirmities occurring have come through some celestial things, it behooves the physician who predicts them [to know] this. This word, indeed, shows that Hippocrates knew and understood the infirmities coming from the celestial bodies, and because of this he said that this science is not a small art of the medical art. And Galen also studied and examined in his mystery, and he found that the mutations of infirmities follow the course of the moon. And that if on the critical day the moon should examine some fortune of the nativity of the infirm, it will come to him without pain at the end and it will be for the good. And if on that same day it should examine some misfortune, it will be proper. And Galen said such things also in his books on medicine. And likewise Hippocrates, who had spoken before Galen on this reason in his book which he made on the embryo, when he spoke of the creature: why it lives from seven months and not from eight. And I say more, that there is no man so ignorant who does not know that because of the course of the sun, heat and cold are made, and other things which are seen with the eye. Ptolemy, however, was not intent to prove this by judgments but by direct demonstration.

Ptolemy wishes to show us after this word that the sphere of fire and air, which changes through the celestial bodies, changes all things that are among us. For the air, when it changes into heat, either brings us from its operation, and in things that are among us.

Since the sun works with the air in all things existing on the earth.

And that not only do the alterations come to the earth through the four seasons of the year, as in the conceptions of animals, the fruits of trees, the excesses of waters, and the mutations of the bodies of men, but also through the diurnal revolution in which it is contained daily. For through this revolution the earth is heated and chilled, dried and moistened in one and the same way, through the configurations in species—which are formed according to their places from the zenith of our heads. From the moon also likewise: because it is closer to the earth, great power is attributed to it, which brings about mutations in many animate and inanimate things. For the excesses of rivers and the decreases happen through the diminution and augmentation of the moon.

The seas also in its rising and setting are altered. Vegetables likewise and animate things, in whole or in part, find growth and decrease by its augmentation or diminution.

And this is not only because of the mutations which are made through the seasons of the year, such as the generation of animals, the fructification of trees, the swellings of waters, and the mutations of other bodies, but also because of the revolution which the firmament makes once in a day; for it heats and chills, moistens and dries by rule and order, which follows the figures which are similar in the manners of those which are made according to their places from the zenith of our heads. From the moon also likewise, which is closer to the earth, great power is attributed to us, because it brings about mutations in many animate and inanimate things. For the excess of the sea and of rivers and the decreases have these, [and] through this diminution and augmentation they happen. The seas also in its rising and setting are altered. Vegetables likewise and animate things, in whole or in part, find growth or decrease by its augmentation or diminution.

After he said that the sun changes the air, and the air also changes the things which it contains, he said that the sun does not do this for the seasons of the year, but he does it every day in the way that he does it for the seasons of the year. For the sun, when it is directly over our heads, makes the air very hot, and when it is removed, it is much diminished of its heat, just as it does every day, according to whether it is about or far from the middle of the sky rising over the earth. For in the morning it makes the air more tempered, just as it is in the time of spring with respect to the manner which the air itself has during the day. And he wishes to say that in the morning the air is more tempered, for the most part. Likewise, from the middle of the sky it heats the air according to what it is in the time of summer, and from the setting it moistens [it] according to what it is in the time of autumn, and from midnight it cools [it] according to what it is in the time of winter. This, indeed, is a thing which a man can easily understand if he examines how the air sets itself every day. And since it is so, it is manifest that the sun is the greater cause in those things which happen for the seasons of the year, just as is the generation of animals and the fructification of trees, and that for those times it follows the complexion of the air. It is certain also that the sun is the greater cause in changing every day those things which are among us by particular mutations. And Ptolemy investigated until he found a demonstration from the part of the senses that the sun works in things that are among us, and they receive from it mutations and operations: many things, living and non-living. For the waters rightfully grow and decrease just as the augmentation and decrease of the light of the moon; it also changes the mutations of the sea according to the ascent and descent of the moon. Likewise, vegetables and animals grow and diminish in whole or in part according to the augmentation and decrease of the moon.

And that one work gives to another is related as long as the bodies are; one, that is, from another, because they are so much the weaker, and by so much the closer, by so much the stronger. And because of this Ptolemy said that because the moon is around us, it announces to us of itself great power. And it is manifest that living things, such as vegetables and animals, and non-living things, such as waters, fumes, and minerals, receive all the above.