(CG 3/41). [That we cannot find happiness in this life by sharing an angel... (Book 3. God, the End of Creatures) (Summa Contra Gentiles) (Aquinas, Thomas, St.)

AN apparent difficulty may be alleged against what has been said from some words of Augustine, which require careful treatment. He says (De Trinitate, IX, iii): "As the mind gathers knowledge of corporeal things by the senses of the body, so of incorporeal things by itself: therefore it knows itself by itself, because itself is incorporeal." By these words it appears that our mind understands itself by itself, and, understanding itself, understands separately subsistent intelligences, or pure spirits, which would militate against what has been shown above. But it is clear that such is not the mind of Augustine. For he says (De Trinitate, X, ix, 12) of the soul seeking knowledge of itself: "Let it not then seek to find (cernere) itself as though it were absent, but let its care be to discern (discernere) itself as it is present: let it not observe itself as though it did not know itself but let it distinguish itself from that other thing which it has mistaken for itself." Whence he gives us to understand that the soul of itself knows itself as present, but not as distinct from other things; and therefore he says (De Trin. X, x) that some have erred in not distinguishing the soul from things that are different from it. But by the knowledge of a thing in its essence the thing is known as distinct from other things: hence definition, which marks the essence of a thing, distinguishes the thing defined from all other things. Augustine then did not mean that the soul of itself knows its own essence. So then, according to the thought of Augustine, our mind of itself knows itself, inasmuch as it knows concerning itself that it exists: for by the very perceiving of itself to act it perceives itself to be. But it acts of itself. Therefore of itself it knows concerning itself that it exists.

1. But it cannot be said that the soul of itself knows concerning itself what it essentially is. For a cognitive faculty comes to be actually cognisant by there being in it the object which is known. If the object is in it potentially, it knows potentially: if the object is in it actually, it is actually cognisant: if in an intermediate way, it is habitually cognisant. But the soul is always present to itself actually, and never potentially or habitually only. If then the soul of itself knows itself by its essence, it must ever have an intellectual view of itself, what it essentially is, which clearly is not the case.

2 and 3. If the soul of itself knows itself in its essence, every man, having a soul, knows the essence of the soul: which clearly is not the case, for many men have thought the soul to be this or that body, and some have taken it for a number or harmony.

So then, by knowing itself, the soul is led to know concerning separately subsistent intelligences the fact of their existence, but not what they are essentially, which would mean understanding their substances. For whereas we know, either by demonstration or by faith, concerning these pure spirits that they are intelligent subsistent beings, in neither way could we gather this knowledge but for the fact that our soul knows from itself the meaning of intelligent being. Hence we must use our knowledge of the intelligence of our own soul as a starting-point for all that we can know of separately subsistent intelligences. But even granting that by speculative sciences we could arrive at a knowledge of the essence of our own soul, it does not follow that we could thereby arrive at a knowledge of all that is knowable about pure spirits; for our intelligence falls far short of the intelligence of a pure spirit. A knowledge of the essence of our own soul might lead to a knowledge of some remote higher genus of pure spirits: but that would not be an understanding of their substances.