I am not clear that it does.
If God has the power to create matter ex nihilo, then the existence or non-existence of matter does not make God more or less complete, because matter, too, comes to be and therefore participates in existence or “act.” Since God is “existence itself” then anything that comes to be participates in some way in God because God is “existence.” At the Big Bang, God did not become more complete because all the matter of the universe participated in existence, i.e., came to be.
All correct so far.
So his forming or informing matter into various particular entities does not make him more complete in the same way that having different ideas does not make a mind more complete. The mind is complete, which is precisely why ideas can be formed.
Good. I like that. Hang on to it.
If, by analogy, all of creation, including the souls and bodies of human beings are like “thoughts” in the mind of God, then having or not having these thoughts do not make God more or less complete. His completeness allows the thoughts.
Correct. Let’s just say that God, is One and that in a manner we cannot hope to comprehend His " thoughts " are His Oneness, His Goodness, His Existence,etc.
The difference is that when God “thinks,” the objects of his thought can be made more or less actual, more or less existing in reality, which would be the substance (existence) of God.
Here, you are getting into trouble. This is not Thomisim and is contrary to Church Doctrine. God does not " share " his substance. The substance or being of created beings is absolutely " other than " the Being or Substance of God.
Isn’t this what Aquinas meant when he claimed that God is the cause of the being of all things because He is Subsistent Being Itself (ipsum esse subsistens)?
No. " Ipsum Esse Subsistens " means Subsisting Being Itself. And This is not the being of all things. God is His own being, he is Unchangeable, Uniquely One, Undivided, Unshared.
The Being of God is One Thing, the being of creation is something altogether different. If God could be diminished, shared, or divided in his Essence/Existence/ Being, he would not be God. Because in God there is no potency or potentiality to be anything more or less than Pure Being Itself. Above all, Ineffable, Untouched.
Now, since God is being itself by His own essence, created being must be his proper effect…Therefore, as long as a thing has being, so long must God be present to it, according to its mode of being. But being is innermost in each thing and most fundamentally present within all things… Hence it must be that God is in all things and innermostly. (S.T. Ia, 8, 1)
The reason why things are what they are is because each participates in the Being of God, in its own way, or as Aquinas says, “…according to its mode of being.”
I don’t mean to be picky but we have to get things straight. When Thomas uses the word " participates " he means " is caused to be by. " Yes the beings of creation " paticipate " in the Being of God only in the sense that He is their cause in being, not that they share in His Being. The beings of creation have their own being and it is not a part of the Being of God. Their being came to be from no prior existing matter or being - not even God’s.
Thus the human soul, for example, has its own being which properly is the substantial form of the human being. And the human soul, though spiritual ( as God is ) is limited. It is a spiritual Form that has existence and it has a potency for the human body, for which it is the proper substantial form. God on the other hand is Pure Existence, His Essence is His Existence, he does not " have " existence, He is Existence, in Whom there is no potency whatsoever ( as explained above), no potency to be more or less than he is.
God’s creative act, his ongoing causality, etc does not diminish his Existence or Being. And although He is absolutely other than His creation of time, space, and creatures, He operates innermostly in every being, moves it, sustains it, and directs it toward its proper end as its primary cause. Individual beings themselves move/change/act as secondary causes.
Reading Part 1 of the Summa Theologiae should help clearify things. Also see " Aquinas " by Edward Feser.
