It has been some time since my last posting, so I want to make a quick note of context for the following. In the previous chapters, Thomas has discussed the existence, essence, comprehensibility, and essential self-knowledge of God. He now turns to God's knowledge of and relation to all other "things", basically, the foundation of the doctrine of Creation.
Chapter 49: THAT GOD UNDERSTANDS THINGS OTHER THAN HIMSELF [QUOD DEUS COGNOSCIT ALIA A SE]
 From the fact that God understands Himself primarily and essentially we must posit that He knows in Himself things other than Himself.
This is a remarkable inference to make, since the thesis of the previous chapter was "that God primarily and essentially knows only Himself"! Let us follow the Doctor's dialectic….
 An effect is adequately known when its cause is known. So “we are said to know each thing when we know the cause.” But God Himself is through His essence the cause of being for other things. Since He has a most full knowledge of His essence, we must posit that God also knows other things [as their cause].
 Moreover, the likeness of every effect somehow preexists in its cause; for every agent produces its like. But whatever is in something is in it according to the mode of that in which it is. If, then, God is the cause of certain things, since according to His nature He is intellectual, the likeness of what He causes will exist in Him in an intelligible way. …
If the objects of God's power were unintelligible––such as a square triangle or a past event that had never happened or, yes, a rock so large that God could not move it––, not just to Him, but essentially intelligible, then they would not be objects of His power. Unreal objects can not be effected, much less generated. Since, however, God knows the likeness of existential power which everything has with His own essential being––i.e. God can "see Himself qua being in all things qua intelligible"––, then God knows those things in the knowledge of His existent power of existence.
 Again, whoever knows perfectly a given thing knows whatever can be truly said of it and whatever befits it according to its nature. But it befits God according to His nature to be the cause of other things. Since, then, God knows Himself perfectly, He knows Himself to be a cause. This cannot be unless He somehow knows what He causes. …
This ties in with the point above.
 If we put together these two conclusions, it appears that God knows Himself as primarily and essentially known, whereas He knows other things as seen in His essence.
 This truth is expressly taught by Dionysius…: “In seeing them, God does not insert Himself in singulars, but He knows them as contained within a single cause” [De div. nom. VII, 2]. And later on: “the divine wisdom, knowing itself, knows other things.”
 To this judgment, too, the authority of Sacred Scripture bears witness. For it is said of God in the Psalms (101:20): “He looked forth from His high sanctuary”; as though to say that God sees other things from His own height.
While flying from Cebu to Camiguin in the Phlippines a few years ago, I was pondering special relativity and how, the higher one gets, the relatively slower things move. From an infinite distance, therefore, one would see all things in perfect stasis. The key is not to think of God's vision as "really good eyesight", but rather as a form of "ontic intuition" in every nook and cranny of existent reality, which sees, as it were, its own being immediately in those nooks and crannies. This intuition, this non-focal vision, is infinite precisely because it suffuses the extent of being. It is infinite in scope not because it is far from all things and takes them all in, but because it is so close to all things and thus takes them all in as single power of being. Consider what St Athanasius writes in De Decretis (HT to Siris, my emphasis):
For God creates, and to create is also ascribed to men; and God has being, and men are said to be, having received from God this gift also. Yet does God create as men do? or is His being as man’s being? Perish the thought; we understand the terms in one sense of God, and in another of men. … [M]en, being incapable of self-existence, are enclosed in place, and consist in the Word of God; but God is self-existent, enclosing all things, and enclosed by none; within all according to His own goodness and power, yet without all in His proper nature.
Chapter 50: THAT GOD HAS A PROPER KNOWLEDGE OF ALL THINGS [QUOD DEUS HABET PROPRIAM COGNITIONEM DE OMNIBUS REBUS]
 …it remains for us to show that God knows all other things as they are distinct from one another and from Himself. This is to know things according to their proper natures.
 In order to show this point, let us suppose that God is the cause of every being…. Now, when the cause is known, the effect is known. … By knowing Himself, God knows whatever proceeds from Him immediately. When this is known, God once more knows what proceeds from it immediately; and so on for all intermediate causes down to the last effect. Therefore, God knows whatever is found in reality. But this is to have a proper and complete knowledge of a thing, namely, to know all that there is in that thing…. Therefore, God has a proper knowledge of things, in so far as they are distinct from one another.
 Furthermore, whatever acts through an intellect knows what it does according to the proper nature of its work; for the knowledge of the maker determines the form for the thing made. Now, God causes things through His intellect, since His being is His understanding and each thing acts in so far as it is in act. …
As the annotated edition remarks: "Since the Creator is an understanding, He understands whatever He gives being to; and giving being to each thing in particular, He understands each in particular."
 Moreover, the distinction of things cannot be from chance, because it has a fixed order. … It cannot be from the intention of a cause acting through a necessity of nature, for nature is determined to one course of action, and thus the intention of no thing acting through the necessity of nature can terminate in many effects in so far as these are distinct. It remains, then, that distinction in things comes from the intention of a knowing cause. … Now, the universal distinction of things cannot be from the intention of some secondary cause, because all such causes belong to the world of distinct effects. It belongs to the first cause, that is through itself distinguished from all other things, to aim at the distinction of all things. God, therefore, knows things as distinct.
The annotated edition explains: "This merely means that physical causes act without any definite intention on their part of any particular results to follow from their action. Electrical tension in the air tends to discharge itself in the form of lightning, but not to kill this particular man under the tree, although it does kill. The volcanic nisus prompts to an eruption, but not to the destruction of such and such a city that is built over the volcano."
I recently discussed the order of natural beings and causal finality in this post at FCA, and this section is an interesting textual sidelight. Insofar as art is aimed a diversity of ends, achievable by a range of means, it differs from nature per se, which is necessarily inclined to its own proper end. Thomas' point is that, given a "necessarily monocausal" entity, it will result in a single state of affairs. But the world is not characterized by a single state of affairs, but by formal distinctions, and therefore nature is not self-organized, but subject in its unified diversity to an intelligent guide, God. Thomas will discuss these points at length in II, 39–45, but you'll just have to wait a while till I get to it!
 Again, whatever God knows He knows most perfectly. For, as was shown above, there is all perfection in God as in the absolutely perfect being. … Since, then, by knowing His own essence God knows things in a universal way, He must also have a proper knowledge of things.
 Then, too, whoever knows a certain nature knows the essential accidents of that nature. The essential accidents of being as being are one and many, as is proved in Metaphysics IV . If, then, by knowing His essence, God knows the nature of being in a universal way, it follows that He knows multitude. But multitude cannot be understood without distinction. Therefore, God knows things as they are distinct from one another.
Cf. I, 50, 9, below.
 Whoever, furthermore, perfectly knows a universal nature knows the mode in which that nature can be possessed. In the same way, he who knows whiteness knows that which receives it more and less. … If, then, by knowing Himself, God knows the universal nature of being, and this not imperfectly, … God must know all grades of beings. …
 Furthermore, he who knows something perfectly knows all that is in it. But God knows Himself perfectly. Therefore, He knows all that is in Him according to His active power. But all things, in their proper forms, are in Him according to His active power, since God is the principle of every being. Therefore, God has a proper knowledge of all things.
 Again, he who knows a certain nature knows whether that nature is communicable. He who did not know that the nature of animal is communicable to many would not know it perfectly. Now, the divine nature is communicable by likeness. God, therefore, knows in how many modes there can be something like His essence. But the diversities of forms arise from the fact that things imitate the divine essence diversely; and so the Philosopher has called a natural form “something divine.” Therefore, God has a knowledge of things in terms of their proper forms.
Cf. I, 50, 6 and I, 49, 3 with gloss, above. To know the fullness of being is to know every possible mode and instance of being. As God perfectly knows Himself qua Pure Being, He knows all things by virtue of their diversely properly likeness to Him qua co-be-ings.
The annotated edition has a note worthy of much consideration:
This is an important principle, often laid down as follows: -- God knows His own nature in all the various modes in which that nature can be copied outside Himself In knowing this, He knows the ideal order, every detail and all inter-relations of details in any possible universe. This is called the knowledge of simple understanding, inasmuch as it is the knowledge of all creatable creatures and their ongoings, antecedent to and apart from the creation and actual existence of any: this knowledge however dwells only in the ideal order of possibilities, and may therefore be called general and universal, though not abstract, inasmuch as it deals with types of individual things, but not with particular existences in rerum natura as actually existing, but only as potentialities. God further knows things outside Himself as they actually and individually exist, inasmuch as all things are of His causation and creation, and exist and act under His will and power. He knows them by insight of Himself, not as He is a mere nature, but as He is a nature willing to create on these particular lines. This knowledge of the universe as the universe actually is for all time, is called the knowledge of vision. For these two knowledges sec Chap. LXVI. The knowledge of simple understanding is not abstract, inasmuch as God knows, not only types of species, but types of different individuals possible in each species; and all these several types He knows, not by so many several ideas, but in the one act by which He knows Himself.
 Moreover, men and other knowing beings know things as distinct from one another in their multitude. If, then, God does not know things in their distinction, it follows that He is the most foolish being of all, as He must have been for those who held that God did not know strife, a thing known to all––an opinion that the Philosopher considers to be untenable in De anima I and Metaphysics III .
Or the more recent "arguments" by atheists that God cannot be omniscient since, lacking hands, He cannot have the know-how to do a handstand, or, lacking hands, cannot know what it feels like to strangle someone, or, being Truth, cannot know the feeling of lying, and so on. Sigh.
 We likewise receive this teaching from the canonic Scriptures. For it is said in Genesis (1:31): “And God saw all things that He had made, and they were very good.” And in Hebrews (4:13): “Neither is there any creature invisible in His sight: but all things are naked and open to His eyes.”
Notice the link in Gen 1:31 between having been made––being––and being good. As truth is the known proper order of all things, the integrated goodness of "all things" in God's knowledge once more signals the convertibility of being, goodness, and truth.