Wherefore S. Augustine (De Ciuitate Dei, V), where he resolves a certain question of two brothers who fell ill and were cured simultaneously, approves the reasoning of Hippocrates rather than that of an Astronomer. For Hippocrates answered that it is owing to the similarity of their humours; and the Astronomer answered that it was owing the identity of their horoscopes. For the Physician’s answer was better, since he adduced the more powerful and immediate cause. Thus, therefore, it must be said that the influence of the stars is to some degree conducive to the wickedness of witches, if it be granted that there is any such influence over the bodies that predisposes them to this manner of abomination rather than to any other sort of works either vicious or virtuous: but this disposition must not be said to be necessary, immediate, and sufficient, but remote and contingent.
Neither is that objection valid which is based on the book of the Philosophers on the properties of the elements, where it says that kingdoms are emptied and lands depopulated at the conjunction of Jupiter and Saturn; and it is argued from this that such things are to be understood as being outside the free will of men, and that therefore the influence of the stars has power over free will. For it is answered that in this saying the Philosopher does not mean to imply that men cannot resist the influence of that constellation towards dissensions, but that they will not. For Ptolemy in Almagest138 says: A wise man will be the master of the stars.139 For although, since Saturn has a melancholy and bad influence and Jupiter a very good influence, the conjunction of Jupiter and Saturn can dispose men to quarrels and discords; yet, through free will, men can resist that inclination, and very easily with the help of God’s grace.
And again it is no valid objection to quote S. John Damascene140 where he says (Book II, chap. VI) that comets are often the sign of the death of kings. For it will be answered that even if we follow the opinion of S. John Damascene, which was, as is evident in the book referred to, contrary to the opinion of the Philosophic Way, yet this is no proof of the inevitability of human actions. For S. John considers that a comet is not a natural creation, nor is it one of the stars set in the firmament; wherefore neither its significance nor influence is natural. For he says that comets are not of the stars which were created in the beginning, but that they are made for a particular occasion, and then dissolved, by Divine command. This then is the opinion of S. John Damascene. But God by such a sign foretells the death of kings rather than of other men, both because a king is a public person, and because from this may arise the confusion of a kingdom. And the Angels are more careful to watch over kings for the general good; and kings are born and die under the ministry of Angels.
And there is no difficulty in the opinion of the Philosophers, who say that a comet is a hot and dry conglomeration, generated in the higher part of space near the fire, and that a conjoined globe of that hot and dry vapour assumes the likeness of a star. But unincorporated parts of that vapour stretch in long extremities joined to that globe, and are a sort of adjunct to it. And according to this view, not of itself but by accident, it predicts death which proceeds from hot and dry infirmities. And since for the most part the rich are fed on things of a hot and dry nature, therefore at such times many of the rich die; among which the death of kings and princes is the most notable. And this view is not far from the view of S. John Damascene, when carefully considered, except as regards the operation and cooperation of the Angels, which not even the philosophers can ignore. For indeed when the vapours in their dryness and heat have nothing to do with the generation of a comet, even then, for reasons already set out, a comet may be formed by the operation of an Angel.
In this way the star which portended the death of the learned S. Thomas was not one of the stars set in the firmament, but was formed by an Angel from some convenient material, and, having performed its office, was again dissolved.
From this we see that, whichever of those opinions we follow, the stars have no inherent influence over the free will, or, consequently, over the malice and character of men.
It is to be noted also that Astronomers often foretell the truth, and that their judgements are for the most part effective on one province or one nation. And the reason is that they
