Mark 1:24

Impure spirits knew that Jesus Christ would come, they had heard of His coming from the angels, they had heard of it from the prophets, and they expected it. For if they were not expecting it, why did they exclaim, "What have we to do with Thee? Art Thou come before the time to destroy us? We know who Thou art; the Holy One of God." They expected that He would come, but they were ignorant of the time.

Those words show clearly that the demons had much knowledge, but entirely lacked love. They dreaded receiving their punishment from him. They did not love the righteousness that was in him. He made himself known to them to the extent he willed; and he willed to be made known to the extent that was fitting. But he was not made known to them as he is known to the holy angels, who enjoy participation in his eternity, in that he is the Word of God. To the demons he is known as he had to be made known, by striking terror into them, for his purpose was to free from their tyrannical power all who were predestined for his kingdom and glory, which is eternally true and truly eternal. Therefore, he did not make himself known to the demons as the life eternal, and the unchangeable light which illuminates his true worshipers, whose hearts are purified by faith in him so that they see that light. He was known to the demons through certain temporal effects of his power, the signs of his hidden presence, which could be more evident to their senses, even those of malignant spirits, than to the weak perception of human beings.

(de Civ. Dei, ix. 21) Moreover, how great is the power which the lowliness of God, appearing in the form of a servant, has over the pride of devils, the devils themselves know so well, that they express it to the same Lord clothed in the weakness of flesh. For there follows, And he cried out, saying, What have we to do with thee, Jesus of Nazareth, &c. For it is evident in these words that there was in them knowledge, but there was not charity; and the reason was, that they feared their punishment from Him, and loved not the righteousness in Him. (ubi sup.) For He was known to them in that degree in which He wished to be known; and He wished as much as was fitting. He was not known to them as to the holy Angels, who enjoy Him by partaking of His eternity according as He is the Word of God; but as He was to be made known in terror, to those beings from whose tyrannical power He was about to free the predestinate. He was known therefore to the devils, not in that He is eternal Life, but by some temporal effects of His Power, which might be more clear to the angelic senses of even bad spirits than to the weakness of men.

(Vict. Ant. e Cat. in Marc.) Or else the devil so speaks, as if he said, 'by taking away uncleanness, and giving to the souls of men divine knowledge, Thou allowest us no place in men.' (Vict. Ant. e Cat. in Marc.) As if he said, Methinks that Thou art come; for he had not a firm and certain knowledge of the coming of God. But he calls Him holy not as one of many, for every prophet was also holy, but he proclaims that He was the One holy; by the article in Greek he shows Him to be the One, but by his fear he shows Him to be Lord of all.

(in Marc. i. 7) Since by the envy of the devil death first entered into the world, it was right that the medicine of healing should first work against the author of death; and therefore it is said, And there was in their synagogue a man, &c.