Reply Obj. 3: The creature is darkness in comparison with the excellence of the Divine light; and therefore the creature's knowledge in its own nature is called "evening" knowledge. For the evening is akin to darkness, yet it possesses some light: but when the light fails utterly, then it is night. So then the knowledge of things in their own nature, when referred to the praise of the Creator, as it is in the good angels, has something of the Divine light, and can be called evening knowledge; but if it be not referred to God, as is the case with the demons, it is not called evening, but "nocturnal" knowledge. Accordingly we read in Gen. 1:5 that the darkness, which God separated from the light, "He called night."
Reply Obj. 4: All the angels had some knowledge from the very beginning respecting the mystery of God's kingdom, which found its completion in Christ; and most of all from the moment when they were beatified by the vision of the Word, which vision the demons never had. Yet all the angels did not fully and equally apprehend it; hence the demons much less fully understood the mystery of the Incarnation, when Christ was in the world. For, as Augustine observes (De Civ. Dei ix, 21), "It was not manifested to them as it was to the holy angels, who enjoy a participated eternity of the Word; but it was made known by some temporal effects, so as to strike terror into them." For had they fully and certainly known that He was the Son of God and the effect of His passion, they would never have procured the crucifixion of the Lord of glory.
Reply Obj. 5: The demons know a truth in three ways: first of all by the subtlety of their nature; for although they are darkened by privation of the light of grace, yet they are enlightened by the light of their intellectual nature: secondly, by revelation from the holy angels; for while not agreeing with them in conformity of will, they do agree, nevertheless, by their likeness of intellectual nature, according to which they can accept what is manifested by others: thirdly, they know by long experience; not as deriving it from the senses; but when the similitude of their innate intelligible species is completed in individual things, they know some things as present, which they previously did not know would come to pass, as we said when dealing with the knowledge of the angels (Q. 57, A. 3, ad 3). _______________________
SECOND ARTICLE [I, Q. 64, Art. 2]
Whether the Will of the Demons Is Obstinate in Evil?
Objection 1: It would seem that the will of the demons is not obstinate in evil. For liberty of will belongs to the nature of an intellectual being, which nature remains in the demons, as we said above (A. 1). But liberty of will is directly and firstly ordained to good rather than to evil. Therefore the demons' will is not so obstinate in evil as not to be able to return to what is good.
Obj. 2: Further, since God's mercy is infinite, it is greater than the demons' malice, which is finite. But no one returns from the malice of sin to the goodness of justice save through God's mercy. Therefore the demons can likewise return from their state of malice to the state of justice.
Obj. 3: Further, if the demons have a will obstinate in evil, then their will would be especially obstinate in the sin whereby they fell. But that sin, namely, pride, is in them no longer; because the motive for the sin no longer endures, namely, excellence. Therefore the demon is not obstinate in malice.
Obj. 4: Further, Gregory says (Moral. iv) that man can be reinstated by another, since he fell through another. But, as was observed already (Q. 63, A. 8), the lower demons fell through the highest one. Therefore their fall can be repaired by another. Consequently they are not obstinate in malice.
Obj. 5: Further, whoever is obstinate in malice, never performs any good work. But the demon performs some good works: for he confesses the truth, saying to Christ: "I know Who Thou art, the holy one of God" (Mark 1:24). "The demons" also "believe and tremble" (James 2:19). And Dionysius observes (Div. Nom. iv), that "they desire what is good and best, which is, to be, to live, to understand." Therefore they are not obstinate in malice.