Thomas Aquinas

“ Further, the intellect precedes the will, for the object of the will is only the good understood. If therefore original sin infects all the powers of the soul, it seems that it must first of all infect the intellect, as preceding the others. ”

“ Further, no wise man pours a precious liquid into a vessel, knowing that the vessel will corrupt the liquid. But the rational soul is more precious than any liquid. If therefore the soul, by being united with the body, could be corrupted with the infection of original sin, God, Who is wisdom itself, would never infuse the soul into such a body. And yet He does; wherefore it is not corrupted by the flesh. Therefore original sin is not in the soul but in the flesh. ”

“ Even original justice pertained radically to the essence of the soul, because it was God's gift to human nature, to which the essence of the soul is related before the powers. For the powers seem to regard the person, in as much as they are the principles of personal acts. ”

“ The corruption of original sin is nowise caused by God, but by the sin alone of our first parent through carnal generation. And so, since creation implies a relation in the soul to God alone, it cannot be said that the soul is tainted through being created. On the other hand, infusion implies relation both to God infusing and to the flesh into which the soul is infused. And so, with regard to God infusing, it cannot be said that the soul is stained through being infused ”

“ I answer that, Those corruptions especially are said to be infectious, which are of such a nature as to be transmitted from one subject to another: hence contagious diseases, such as leprosy and murrain and the like, are said to be infectious. ”