Theology of St. Thomas - On the Nature of God's Knowledge

There is no sense in which there is sequence or succession in God's knowledge.

In the divine knowledge there is no discursion; the proof of which is as follows. In our knowledge there is a twofold discursion: one is according to succession only, as when we have actually understood anything, we turn ourselves to understand something else; while the other mode of discursion is according to causality, as when through principles we arrive at the knowledge of conclusions. The first kind of discursion cannot belong to God. For many things, which we understand in succession if each is considered in itself, we understand simultaneously if we see them in some one thing; if, for instance, we understand the parts in the whole, or see different things in a mirror. Now God sees all things in one (thing), which is Himself. Therefore God sees all things together, and not successively. Likewise the second mode of discursion cannot be applied to God.

First, because this second mode of discursion presupposes the first mode; for whosoever proceeds from principles to conclusions does not consider both at once; secondly, because to discourse thus is to proceed from the known to the unknown. Hence it is manifest that when the first is known, the second is still unknown; and thus the second is known not in the first, but from the first. Now the term discursive reasoning is attained when the second is seen in the first, by resolving the effects into their causes; and then the discursion ceases. Hence as God sees His effects in Himself as their cause, His knowledge is not discursive (ST I Q14 A7).

God's knowledge is perfect and complete. It is immutable just as he is himself. In another post [get link to the post on perfection] I said that there is no way that we can cause a reaction in God, as (for example) to anger him; this is a consequence of the fact that he is perfect. Related to this is that his knowledge is as immutable as he is himself, so that he knows from before creation all our actions. Consequently those passages of the Bible - like, for example, Gen. 22:12 - which seem to show God "learning" something ("I know now that you fear God...") can only be anthropomorphisms. The Lord God knew exactly how Abraham would respond to the command to sacrifice Isaac from all eternity. In the same way, he knows us completely. There is nothing hidden from him; he knows our inmost thoughts and our "secret" sins.