I answer that, Some have maintained that the demons were wicked straightway in the first instant of their creation; not by their nature, but by the sin of their own will; because, as soon as he was made, the devil refused righteousness. To this opinion, as Augustine says (De Civ. Dei xi, 13), if anyone subscribes, he does not agree with those Manichean heretics who say that the devil's nature is evil of itself. Since this opinion, however, is in contradiction with the authority of Scripture---for it is said of the devil under the figure of the prince of Babylon (Is. 14:12): "How art thou fallen . . . O Lucifer, who didst rise in the morning!" and it is said to the devil in the person of the King of Tyre (Ezech. 28:13): "Thou wast in the pleasures of the paradise of God," ---consequently, this opinion was reasonably rejected by the masters as erroneous.
Hence others have said that the angels, in the first instant of their creation, could have sinned, but did not. Yet this view also is repudiated by some, because, when two operations follow one upon the other, it seems impossible for each operation to terminate in the one instant. Now it is clear that the angel's sin was an act subsequent to his creation. But the term of the creative act is the angel's very being, while the term of the sinful act is the being wicked. It seems, then, an impossibility for the angel to have been wicked in the first instant of his existence.
This argument, however, does not satisfy. For it holds good only in such movements as are measured by time, and take place successively; thus, if local movement follows a change, then the change and the local movement cannot be terminated in the same instant. But if the changes are instantaneous, then all at once and in the same instant there can be a term to the first and the second change; thus in the same instant in which the moon is lit up by the sun, the atmosphere is lit up by the moon. Now, it is manifest that creation is instantaneous; so also is the movement of free-will in the angels; for, as has been already stated, they have no occasion for comparison or discursive reasoning (Question [58], Article [3]). Consequently, there is nothing to hinder the term of creation and of free-will from existing in the same instant.
We must therefore reply that, on the contrary, it was impossible for the angel to sin in the first instant by an inordinate act of free-will. For although a thing can begin to act in the first instant of its existence, nevertheless, that operation which begins with the existence comes of the agent from which it drew its nature; just as upward movement in fire comes of its productive cause. Therefore, if there be anything which derives its nature from a defective cause, which can be the cause of a defective action, it can in the first instant of its existence have a defective operation; just as the leg, which is defective from birth, through a defect in the principle of generation, begins at once to limp. But the agent which brought the angels into existence, namely, God, cannot be the cause of sin. Consequently it cannot be said that the devil was wicked in the first instant of his creation.
