Whether Even Vices Themselves as Objects of Intellectual Apprehension are to Be Preferred to Light as an Object of Sense Perception, and are to Be Attributed to God as Their Author. Vice of the Mind and Certain Defects are Not Rightly to Be Counted Among Intelligible Things. Defects Themselves Even If They Should Be Counted Among Intelligible Things Should Never Be Put Before Sensible Things. If Light is Visible by God, Much More is the Soul, Even If Vicious, Which in So Far as It Lives is an Intelligible Thing. Passages of Scripture are Adduced by the Manichæans to the Contrary
8 This being the case, who will dare, while attributing sun and moon, and whatever is refulgent in the stars, nay in this fire of ours and in this visible earthly life, to God, to decline to grant that any souls whatsoever, which are not souls except by the fact of their being perfectly alive, since in this fact alone life has the precedence of light, are from God. And since he speaks truth who says, In as far as a thing shines it is from God, would I speak falsely, mighty God, if I should say, In so far as a thing lives it is from God? Let not, I beseech you, blindness of intellect and perversions of mind be increased to such an extent that men may fail to know these things. But however great their error and pertinacity might have been, trusting in these arguments and armed therewith, I believe that when I should have laid the matter before them thus considered and canvassed, and should have calmly conferred with them, I should have feared lest any one of them should have seemed to me to be of any consequence, should he endeavor to subordinate or even to compare to bodily sense, or to those things that pertain to bodily sense as objects of knowledge, either intellect or those things that are perceived (not by way of defect) by the intellect. Which point having been settled, how would he or any other have dared to deny that such souls as he would consider evil, yet since they are souls, are to be reckoned in the number of intelligible things, nor are objects of intellectual perception by way of defect? This is on the supposition that souls are souls only by being alive. For if they were intellectually perceived as vicious through defect, being vicious by lack of virtue, yet they are perceived as souls not through defect, for they are souls by reason of being alive. Nor can it be maintained that presence of life is a cause of defect, for by as much as anything is defective, by so much is it severed from life.
9. Since therefore it would have been every way evident that no souls can be separated from that Author from whom yonder light is not separated, whatever they might have now adduced I should not have accepted, and should rather have admonished them that they should choose with me to follow those who maintain that whatever is, since it is, and in whatever degree it is, has its existence from the one God.
Source: On Two Souls, Against the Manichaeans (New Advent)