Reply Obj. 1: The spiritual substances, that move the heavenly bodies, do indeed act on corporeal things by means of the heavenly bodies; but they act immediately on the human intellect by enlightening it. On the other hand, they cannot compel the will, as stated above (Q. 111, A. 2).
Reply Obj. 2: Just as the multiformity of corporeal movements is reducible to the uniformity of the heavenly movement as to its cause: so the multiformity of actions proceeding from the intellect and the will is reduced to a uniform principle which is the Divine intellect and will.
Reply Obj. 3: The majority of men follow their passions, which are movements of the sensitive appetite, in which movements of the heavenly bodies can cooperate: but few are wise enough to resist these passions. Consequently astrologers are able to foretell the truth in the majority of cases, especially in a general way. But not in particular cases; for nothing prevents man resisting his passions by his free-will. Wherefore the astrologers themselves are wont to say that "the wise man is stronger than the stars" [*Ptolemy, Centiloquium, prop. 5], forasmuch as, to wit, he conquers his passions. _______________________
FIFTH ARTICLE [I, Q. 115, Art. 5]
Whether Heavenly Bodies Can Act on the Demons?
Objection 1: It would seem that heavenly bodies can act on the demons. For the demons, according to certain phases of the moon, can harass men, who on that account are called lunatics, as appears from Matt. 4:24 and 17:14. But this would not be if they were not subject to the heavenly bodies. Therefore the demons are subject to them.
Obj. 2: Further, necromancers observe certain constellations in order to invoke the demons. But these would not be invoked through the heavenly bodies unless they were subject to them. Therefore they are subject to them.
Obj. 3: Further, heavenly bodies are more powerful than inferior bodies. But the demons are confined to certain inferior bodies, namely, "herbs, stones, animals, and to certain sounds and words, forms and figures," as Porphyry says, quoted by Augustine (De Civ. Dei x, 11). Much more therefore are the demons subject to the action of heavenly bodies.
On the contrary, The demons are superior in the order of nature, to the heavenly bodies. But the "agent is superior to the patient," as Augustine says (Gen. ad lit. xii, 16). Therefore the demons are not subject to the action of heavenly bodies.
I answer that, There have been three opinions about the demons. In the first place the Peripatetics denied the existence of demons; and held that what is ascribed to the demons, according to the necromantic art, is effected by the power of the heavenly bodies. This is what Augustine (De Civ. Dei x, 11) relates as having been held by Porphyry, namely, that "on earth men fabricate certain powers useful in producing certain effects of the stars." But this opinion is manifestly false. For we know by experience that many things are done by demons, for which the power of heavenly bodies would in no way suffice: for instance, that a man in a state of delirium should speak an unknown tongue, recite poetry and authors of whom he has no previous knowledge; that necromancers make statues to speak and move, and other like things.