Question 12 in Summa Theologiae is “how God is known by his creatures.”
I already summarized Article 1 (Can any created mind see the essence of God?).
Article 2. Does the mind see the essence of God by means of any created likeness?
Aquinas notes that in 1 John 3.2, “We know that when he [God] appears we shall be like him and we shall know him just as he is.” (1a, 12, 2, 1) Further, Augustine comments that “When we know God a likeness of him comes to be in us.” (De Trinitate IX, 11)
When we think or sense something (in order to know something), we rely on the likeness of the thing we are trying to know.
“Hence,” Aquinas says, “if God is actually seen by the created mind he must be seen through some likeness.” (1a, 12, 2, 3)
But, in contrast to this, Paul writes about how we perceive reality “in a mirror by dull reflection.” Here, according to Augustine, Paul is saying that the mirror that offers a dull reflection to us is “any likeness that may help us to understand God.” (De Trinitate IX, 11)
Aquinas supposes that if we are really to see the essence of God, as God actually is in himself, then we would not be looking into a mirror that is dull. If we look into a mirror, we are not seeing the a real thing, but a reflection of the thing. If one does not look at God in his fullness, then one is not really seeing God. If one sees God, one does not see him through a mirror that is a dull reflection because then one would simply be looking at a image of God, but not God in himself. “But to see God in his essence is not to see him ‘in a dull mirror’ but is contrasted with this; hence the divine essence is not seen through any likeness.” (1a, 12, 2, Contra)
Aquinas talks about how for us to see something, we have to have the faculty of sight and the thing that we are looking at needs to be in view. The essence of the thing we are looking at is not in the faculty of sight. When one looks at a rock, the rock is not actually in our eyes; we are just seeing an image of the rock.
How does this relate to our seeing of God’s essence?
First, Thomas proposes that God is both the source of sight (understanding, contemplation) and the object of sight (object isn’t the best word, but it works for now). “Now it is clear that God is the author of the power of understanding and also can be an object of understanding.” (1a, 12, 2, Reply to Contra)
Metaphorically, one would say that God is both the source of light that illuminates the way to himself and the light which one seeks. This means that our mind relies on some likeness to God. We need light to see God who is light.
(I am a still bit shaky on this argument of Aquinas’)
“When, however, we consider the essence of God as an object of sight, it is impossible that it should be united with the power of sight by any created image.” (1a, 12, 2, Reply to Contra)
Referring to Dionysius, Aquinas notes three points:
First, “we cannot even know the essences of incorporeal things through bodily likenesses, much less could we see the essence of God through any kind of created likeness.” (1a, 12, 2, Reply to Contra)
This means that we cannot know the abstract thing as it really is (its essence) through a concrete object. E.g., we might catch glimpses of what love is through the bodily communication between two lovers, but that doesn’t mean that we know what love is in its essence.
Why then do we assume that we can somehow grasp God’s essence through created things?
Second, “the essence of God is to exist, and since this could not be the case with any created form no such form could represent the essence of God to the understanding.” (1a, 12, 2, Reply to Contra)
God’s essence is his existence. Created things have essence and existence, but they are not one and the same. Created things also derive their existence from God who sustains everything in existence.
Created things participate in the essence of God, to the extent that they derive their existence from God.
Created things’ essence is not the same as their existence. (Unlike God)
Third, “the divine essence is beyond description, containing to a transcendent degree every perfection that can be described or understood by the created mind.” (1a, 12, 2 Reply to Contra)
Time to find a good commentary on Aquinas!
Aquinas concludes that in order to comprehend God’s essence, we have to have some likeness to him, that is, the gift of sight that is given from God to our mind. “It is not that God’s essence can e seen b means of any created likeness representing him as he is.” (1a, 12, 2, Reply to Contra)
The likeness we bear to God is not created, but is divine grace.
I have to admit that this article was a bit over my head in some places. Like I said, time to find a good commentary that can explain this a bit more clearly to me.