Thomas Aquinas

“ Further, all corruption results from some movement. But the habit of science, which is in the soul, cannot be corrupted by a direct movement of the soul itself, since the soul is not moved directly. It is, however, moved indirectly through the movement of the body: and yet no bodily change seems capable of corrupting the intelligible species residing in the intellect: since the intellect independently of the body is the proper abode of the species; for which reason it is held that habits are not lost either through old age or through death. Therefore science cannot be corrupted. ”

“ It would seem that a habit cannot be corrupted. For habit is within its subject like a second nature; wherefore it is pleasant to act from habit. Now so long as a thing is, its nature is not corrupted. Therefore neither can a habit be corrupted so long as its subject remains. ”

“ Consequently all habits that are gradually undermined by contrary agencies which need to be counteracted by acts proceeding from those habits, are diminished or even destroyed altogether by long cessation from act, as is clearly seen in the case both of science and of virtue. For it is evident that a habit of moral virtue makes a man ready to choose the mean in deeds and passions. ”