Thomas Aquinas - Summa Theologica, Part I-II (Pars Prima Secundae)

On the contrary, Damascene says (De Fide Orth. ii, 7) that "the heavenly bodies are not the causes of our acts." But they would be, if the will, which is the principle of human acts, were moved by the heavenly bodies. Therefore the will is not moved by the heavenly bodies.

I answer that, It is evident that the will can be moved by the heavenly bodies in the same way as it is moved by its object; that is to say, in so far as exterior bodies, which move the will, through being offered to the senses, and also the organs themselves of the sensitive powers, are subject to the movements of the heavenly bodies.

But some have maintained that heavenly bodies have an influence on the human will, in the same way as some exterior agent moves the will, as to the exercise of its act. But this is impossible. For the "will," as stated in De Anima iii, 9, "is in the reason." Now the reason is a power of the soul, not bound to a bodily organ: wherefore it follows that the will is a power absolutely incorporeal and immaterial. But it is evident that no body can act on what is incorporeal, but rather the reverse: because things incorporeal and immaterial have a power more formal and more universal than any corporeal things whatever. Therefore it is impossible for a heavenly body to act directly on the intellect or will. For this reason Aristotle (De Anima iii, 3) ascribed to those who held that intellect differs not from sense, the theory that "such is the will of men, as is the day which the father of men and of gods bring on" [*Odyssey xviii. 135] (referring to Jupiter, by whom they understand the entire heavens). For all the sensitive powers, since they are acts of bodily organs, can be moved accidentally, by the heavenly bodies, i.e. through those bodies being moved, whose acts they are.

But since it has been stated (A. 2) that the intellectual appetite is moved, in a fashion, by the sensitive appetite, the movements of the heavenly bodies have an indirect bearing on the will; in so far as the will happens to be moved by the passions of the sensitive appetite.

Reply Obj. 1: The multiform movements of the human will are reduced to some uniform cause, which, however, is above the intellect and will. This can be said, not of any body, but of some superior immaterial substance. Therefore there is no need for the movement of the will to be referred to the movement of the heavens, as to its cause.

Reply Obj. 2: The movements of the human body are reduced, as to their cause, to the movement of a heavenly body, in so far as the disposition suitable to a particular movement, is somewhat due to the influence of heavenly bodies; also, in so far as the sensitive appetite is stirred by the influence of heavenly bodies; and again, in so far as exterior bodies are moved in accordance with the movement of heavenly bodies, at whose presence, the will begins to will or not to will something; for instance, when the body is chilled, we begin to wish to make the fire. But this movement of the will is on the part of the object offered from without: not on the part of an inward instigation.

Reply Obj. 3: As stated above (Cf. I, Q. 84, AA. 6, 7), the sensitive appetite is the act of a bodily organ. Wherefore there is no reason why man should not be prone to anger or concupiscence, or some like passion, by reason of the influence of heavenly bodies, just as by reason of his natural complexion. But the majority of men are led by the passions, which the wise alone resist. Consequently, in the majority of cases predictions about human acts, gathered from the observation of heavenly bodies, are fulfilled. Nevertheless, as Ptolemy says (Centiloquium v), "the wise man governs the stars"; which is a though to say that by resisting his passions, he opposes his will, which is free and nowise subject to the movement of the heavens, to such like effects of the heavenly bodies.

Or, as Augustine says (Gen. ad lit. ii, 15): "We must confess that when the truth is foretold by astrologers, this is due to some most hidden inspiration, to which the human mind is subject without knowing it. And since this is done in order to deceive man, it must be the work of the lying spirits." ________________________

SIXTH ARTICLE [I-II, Q. 9, Art. 6]

Whether the Will Is Moved by God Alone, As Exterior Principle?

Objection 1: It would seem that the will is not moved by God alone as exterior principle. For it is natural that the inferior be moved by its superior: thus the lower bodies are moved by the heavenly bodies. But there is something which is higher than the will of man and below God, namely, the angel. Therefore man's will can be moved by an angel also, as exterior principle.

Obj. 2: Further, the act of the will follows the act of the intellect. But man's intellect is reduced to act, not by God alone, but also by the angel who enlightens it, as Dionysius says (Coel. Hier. iv). For the same reason, therefore, the will also is moved by an angel.

Obj. 3: Further, God is not the cause of other than good things, according to Gen. 1:31: "God saw all the things that He had made, and they were very good." If, therefore man's will were moved by God alone, it would never be moved to evil: and yet it is the will whereby "we sin and whereby we do right," as Augustine says (Retract. i, 9).

On the contrary, It is written (Phil. 2:13): "It is God Who worketh in us" [Vulg.'you'] "both to will and to accomplish."

I answer that, The movement of the will is from within, as also is the movement of nature. Now although it is possible for something to move a natural thing, without being the cause of the thing moved, yet that alone, which is in some way the cause of a thing's nature, can cause a natural movement in that thing. For a stone is moved upwards by a man, who is not the cause of the stone's nature, but this movement is not natural to the stone; but the natural movement of the stone is caused by no other than the cause of its nature. Wherefore it is said in Phys. vii, 4, that the generator moves locally heavy and light things. Accordingly man endowed with a will is sometimes moved by something that is not his cause; but that his voluntary movement be from an exterior principle that is not the cause of his will, is impossible.

Now the cause of the will can be none other than God. And this is evident for two reasons. First, because the will is a power of the rational soul, which is caused by God alone, by creation, as was stated in the First Part (Q. 90, A. 2). Secondly, it is evident from the fact that the will is ordained to the universal good. Wherefore nothing else can be the cause of the will, except God Himself, Who is the universal good: while every other good is good by participation, and is some particular good, and a particular cause does not give a universal inclination. Hence neither can primary matter, which is potentiality to all forms, be created by some particular agent.

Reply Obj. 1: An angel is not above man in such a way as to be the cause of his will, as the heavenly bodies are the causes of natural forms, from which result the natural movements of natural bodies.

Reply Obj. 2: Man's intellect is moved by an angel, on the part of the object, which by the power of the angelic light is proposed to man's knowledge. And in this way the will also can be moved by a creature from without, as stated above (A. 4).

Reply Obj. 3: God moves man's will, as the Universal Mover, to the universal object of the will, which is good. And without this universal motion, man cannot will anything. But man determines himself by his reason to will this or that, which is true or apparent good. Nevertheless, sometimes God moves some specially to the willing of something determinate, which is good; as in the case of those whom He moves by grace, as we shall state later on (Q. 109, A. 2).