Question Five of Chapter Eight of the Third Decade
From what the reason is to be taken that certain marvels are from the devil and not from God
It is asked: since marvelous apparitions can occur from good and evil causes, as was said immediately above, from what is the distinction of these from those to be taken?
Augustine responds in Book XXI of The City of God, saying that miracles which are effected by God—whether through the merits of saints, through human beings still constituted in the body, through angels, or in other ways—are altogether incomprehensible to mortals.
Therefore, in matters of this sort, the distinction is sometimes so difficult that it cannot adequately be obtained from consideration of the circumstances of place, time, opportunity, modes of acting, the quality of the doers, and the end.
From this, however, he assumes that marvelous and unusual things which are effected through the first three causes concerning the dead, or otherwise, tend toward the honor of God and the salvation of human beings. The other things, which are effected through the last three causes, bring destruction upon those who attend to such things without prudent discernment of spirits.
Hence Augustine says in the book cited above, chapter 10: “Demons perform miracles so that they may be believed to be gods. Holy angels and human beings, however, perform them so that God may be praised.”
These things are from Master Henry of Assia upon Genesis.