"The good of the grace of one soul is greater than the good of the nature of the whole universe"
- St Thomas Aquinas Ia IIa, q.24, a. 3, ad 2
|REALITY—A Synthesis Of Thomistic Thought
by Reginald Garrigou-Lagrange, O. P.
CH9: GOD'S KNOWLEDGE
The next step in the Thomistic synthesis is to apply its fundamental principles to the manner and nature of God's omniscience. The essential points are.
1. God's knowledge in general.
2. God's knowledge of the conditional future.
Article 1: God's Knowledge In General 
Immateriality is the root of knowledge. The more immaterial a being is, the more capable it is of knowing. Now God is altogether immaterial, because He transcends the limits, not of matter merely, but even of essence, since He is infinite in perfection. Hence He is transcendently intelligent. .
Hence God knows Himself, rather, comprehends Himself, since He knows Himself as far as He is knowable, that is, infinitely.  His intellect is not a faculty, distinct from its act and from its object, since He is the self-subsistent act of understanding. Nor does He have to form first an idea of Himself, that is, form an interior accidental concept and word, because His essence is not only actually intelligible, but is subsistent truth, actually and eternally understood.  When revelation tells us that God the Father expresses Himself in His Word, we are meant to understand this as an expression of superabundance, not of indigence. Besides, the divine Word is not, as in us, an accident, but substance. Hence all elements of thought (thinking subject, faculty of thought, actual thinking, idea, and object) are all identified in God, who is pure act. And His actual thinking, far from being an accident, is identified with His substance.  God, says Aristotle, is understanding of understanding, an unmixed intellectual splendor eternally self-subsistent.
How does God know what He Himself is not, that is, realities that are possible, realities that actually exist, and future events? First of all, divine knowledge, cannot, like ours, depend on, be measured by, created things. Such dependence, being passive, is irreconcilable with the perfection of pure act. On the contrary, nothing can be possible, existent, or future except in dependence on essential existence, since it is clear that any conceivable existence outside of the First Cause must necessarily carry with it a relation of dependence on that First Cause. Things other than Himself, says St. Thomas, are known by God not in themselves (by dependence on them): but in Himself.  Whereas we, in order to know God, must look up from below, from the sense world which mirrors God, God, on the contrary, does not have to look down, but knows us there on high, in Himself as mirror. By knowing His own creative power God knows all that He could do if He willed, all that He is doing now, all that He still will do, all that He would do did He not have some higher purpose, all, lastly, that He permits for the sake of a higher good. There is no need of neologisms, of new special terms. The traditional terms of common usage suffice to express well this omniscience of God. In Himself, the creative mirror, God knows all things.
How does God know the possible world, that absolutely numberless and truly infinite multitude of worlds which could exist but never will in fact exist? The answer is: God knows them by knowing the omnipotence of His creative power. .
Further, by knowing what He willed to do in the past and what He wills to do in the future and what He is actually doing now, God knows all things, past, present, and future, all that creatures have done, are doing now, and will do. And all this world of time, past, present, and future, He knows not in general and confusedly, but in particular and distinctly, since from Him, the First Cause, comes all reality, even prime matter, which is the source of all individual differences in the corporeal world. Hence even the minutest particularity in creatures, since it is a reality, depends on God for its existence, even when it gets that existence, not by creation, but by God's concurrence with created causes. But this knowledge, infinitely distinct and particularized, is still not discursive, but intuitive, taking in with one instantaneous glance all that God does or could do. .
This divine knowledge is the cause of things, since it is united to God's free will, which, among all possible things, chooses one particular thing to exist rather than another.  God's knowledge of possible things, since it presupposes no decree of the divine will, is called simple intelligence. But His knowledge of actual things, since it does presuppose such a decree, is called "knowledge of approbation," approbation, not of evil, but of all that is real and good in the created universe.
How then does God know evil? He knows it by its opposition to the good wherein alone evil can exist. Hence God knows evil by knowing what He permits, what He does not hinder.  No evil, physical or moral, can come to be unless, for a higher good, God permits it to be. Knowing what He permits, God knows by that permission all evil that has been, is, or will ever be.
Article 2: God's Knowledge Of The Conditional Future
When God permits evil, what is His will regarding the good opposed to that evil? That good cannot be willed efficaciously, otherwise it would be. But it can be willed by God conditionally. Thus God would wish to preserve the life of the gazelle, did He not will to permit that death for the life of the lion. He would hinder persecution, did He not judge good to permit it for the sanctification of the just and the glory of the martyrs; He would will the salvation of the sinner, Judas, for example, did He not permit his loss as manifestation of divine justice.
Starting from this point, we understand how God knows the conditional future.  God knows all that He would will to be realized, all that He would bring to pass, did He not renounce it for a higher end. Hence God's knowledge of the conditioned future presupposes a conditional decree of God's will. The futuribilia are a medium between a merely possible future and a future really to be. It would be a grave error to confound them with the merely possible. This is the teaching of all Thomists, in opposition to the Molinistic theory, that is, an intermediate knowledge (scientia media): a knowledge, preceding any divine decree, of the conditional future free acts of the creature. This theory, Thomists maintain, leads to admitting in God's knowledge a passivity, dependent on something in the created order. If God does not determine (by His own decree): then He is determined (made to know) by something else. This dilemma seems to Thomists to be insoluble.
As regards the knowledge of the contingent future, of what a free creature, say, will be actually willing a hundred years from now, God knows it not as future, but as present. For this knowledge is not measured by time, does not have to wait until future becomes present. It is measured, as God Himself is measured, by the unchangeable now of eternity, which surrounds  and envelops all other durations. Thus, to illustrate, the culminating point of a pyramid is simultaneously present to all points of its base. An observer, on the summit of a mountain, sees the entire army defiling in the valley below. .
Now it is evident that the event, in itself future, would not be present even in eternity, had not God willed it (if it is good): or permitted it (if it is evil). The conversion of St. Paul is present in eternity only because God willed it, and the impenitence of Judas only because God permitted it.
This knowledge too is intuitive, because it is the knowledge of what God either wills to be or permits to be. God sees His own eternal action, creative or permissive, though the effect of that action is in time, coming into existence at the instant chosen for it by God from eternity. His eternal permissions He sees in relation to that higher good of which He alone is judge.
Our free and salutary acts God sees in His own eternal decision to give us the grace to accomplish those acts. In Himself, in His own creative light, He sees them freely done, under that grace which, far from destroying our liberty, actualizes it, strongly and sweetly,  so that we cooperate with that grace for His glory and our own. This doctrine will become more explicit in the following chapter, where we study God's will and love