Monday, 24 May 2010

Question 14 - God's Knowledge


We've now come to a major division in what is often referred to as the “Treatise on the one God” (QQ. 2-26). Aquinas has talked about God's essence and about how we can know God and about how we can talk about God. It's now time for Aquinas to discuss in more detail the inner life of God. The rest of this treatise is divided into four sections: on God's intellect; on God’s will; on the conjunction of God’s intellect and will; and finally on God's power. This will take us up to the end of the Treatise on the One God, and will lead in to the Treatise on the Triune God.

Question 14 is a long and difficult question that contains topics that are still thoroughly controversial areas of thought in philosophical theology. To help us through this question, we thought it would be a good idea to have both the usual summary guide (this entry) as well as texts of the question concerning knowledge itself rearranged into thematic groups, so that St. Thomas explains his terminology to us in his own words.

Why this Question Matters.

God obviously knows everything. But what does it mean for Him to “know”? How does God’s knowledge differ from our knowledge? The answers for many of the inquiries included in the articles of this question seem obvious: “Yes, of course!” or “Of course not!” However, the point of many of these questions is not the answers themselves, but the way in which we are to understand what the questions mean. By now it should come as no surprise that God’s knowledge must be his essence. But there are some stunning conclusions that follow from this fact: God’s knowledge is creative; God knows all future contingents. Omniscience is larger than it might seem at first.

The Thread of the Argument

A1: It would seem natural to think that God has knowledge in a pre-eminent way, given what we know about God so far. However, since our very concept of knowledge is derived from what we know about creatures, we must remember that when we talk about the knowledge of God we're talking analogously. So, we must think about how God’s knowledge differs in character from our knowledge. According to Aquinas, we have knowledge of a thing when we have some sort of grasp of the form of the thing in our mind. However, the form of the thing that we have in our mind does not inform matter. (Otherwise, knowing something would involve that thing being physically present in our minds!) So, in a certain sense, our capacity to know depends on being free from matter. From this, Aquinas deduces that the freer from matter that a being is, the better the being can know. Since God is immaterial in the highest degree, he has knowledge in the highest degree. Now Aquinas can deal with the objections that are based on the assumption that God’s knowledge is just like our knowledge. To do this, we can think about what a creature’s knowledge consists in, and then eliminate any imperfections. So for example, God's knowledge is a pure actuality; God knows all things “all in one go”; God's knowledge does not come to be, it always is.

A2: To ask whether God understands himself may seem very odd indeed; but Aquinas’s task is to work through the consequences of our analogical understanding of “how God works”. Here Aquinas quotes Aristotle to the effect that when we sense something or when we understand something, the senses and the intellect move from potentiality to actuality with respect to what is sensed or understood respectively. For example, when we understand something our intellect is “informed” by an “intelligible species” (the immaterial form corresponding to the object itself that the mind grasps), moving from potentiality to the actuality of understanding that object. Since God is pure actuality, it immediately follows that He possesses all intelligible species within His intellect (as He cannot be in potentiality to any of them). Since there are no accidental forms in God, it also follows that all of these intelligible species are actually God’s very intellect. So, we can say, in a sense, that God’s intellect encompasses everything that there is. The answer to the second objection points out that although human knowledge involves a potentiality moving to actuality (through learning, for example), God’s intellect is not like this. The reply to the third objection introduces the important notion of the “passive intellect”. Aquinas considered the intellect to be divided into two parts: the “agent intellect” that organises and assimilates the information received from the senses (so it is the “active” part of the intellect) and the “passive intellect” that receives and keeps the intelligible species offered to it by the agent intellect.

A3: Similarly, God has comprehensive knowledge of Himself, in that He knows everything there is to know in the most perfect way possible. This follows from God’s pure actuality. The purpose of this article appears to be to deal with particular objections drawn from the created world that suggest that “comprehending” involves circumscription of a number of things (facts, for example). Since Aquinas believes that there are no actual infinities in the created world (Ia Q7 a4), application of this idea to God would seem to imply that His intellect must be finite in some way. Aquinas deals with these objections (especially in the reply to objection 2) by coming very close the modern notion of one-to-one correspondence in that “God is finite to Himself” is taken as meaning that there is some proportion between God and His intellect! (See the background document on infinity).

A4: We often think of understanding as being an activity, so if we apply that sort of thinking to God it would be difficult to see how His understanding could be His substance. (How could an activity be a substance?) On the contrary, Aquinas insists that understanding is not an activity that proceeds from an agent but rather is a perfection, an actuality, within the agent. Again, as God is pure actuality and within God there are no accidents, God’s understanding must be identical with His substance.

A5: God understand Himself, and clearly He must know things external to Himself, but in what sense? Again, it is tempting to push the analogy between human knowing and divine knowing too far. We might point to the fact that learning adds something to us and contributes to our perfection; if the same happened with God, this would lead to us to conclude that God was added to or perfected by things external to Himself, which is clearly nonsense. Aquinas rejects this parallel, pointing out that as He is the first efficient cause of everything He must know everything in causing it. (Indeed, as His act of being is the same as His act of knowing, article 8 can assert that His act of knowing is itself creative.) Aquinas continues with an important distinction: we can know things through themselves in that we can grasp a thing’s intelligible species through our direct sensation of them; or we can know things indirectly through inference from the parts to a whole or from a reflection in a mirror or through a thing’s effects. When we apply this to God, we realize that God understands Himself through Himself; but also, he sees other things through Himself as well and not in themselves, because His essence already contains those other things in likeness.

A6: The distance between God and created beings is extreme; and God has an awful lot of things to know. Does this mean that He knows things other than Himself only in a general sort of way (“here’s the form of a cow, let’s instantiate two hundred million of them”) or does he know every particular created thing specifically in the sense of what makes one individual different from another? (“This one’s got brown spots, this one’s black and white …”) Scripture is very particular in emphasising that God does know individuals intimately, so the length of Aquinas’s argument here may seem surprising. The reason for this length is that Aquinas is concerned to refute a number of mistaken ideas about God’s knowledge. At the heart of Aquinas’s position is the observation that a generalized sort of knowledge is an imperfect sort of knowledge; we cannot deny perfection in God, therefore God’s knowledge is specific. So we are to believe that things are to be found in God not only as regards what they have in common but also in regards as to what makes them different from one another. Later, in article 11 Aquinas will take this argument further and will show that God knows individuals as specific individuals.

A7: Our knowledge is discursive; that is, we know a lot of things but at any specific instant we can only consider one thing at a time. Similarly, when we think about a particular thing, our thought considers one aspect of that thing at a time. The same is not true of God. He sees everything in one act, with no temporal or logical succession; He sees everything in His substance.

A8: St. Augustine said that “God does not know all creatures because they exist; they exist because He knows them”. In this article, Aquinas will hand on this teaching that God’s knowledge is causal, with the image of God as the artist producing the work of art. Since His intellect is the same as His act of knowing, His knowing is causative. Now, knowledge of the work of art to be produced involves the intelligible species of that thing existing in the intellect. But an intelligible species existing in the intellect doesn’t necessarily cause the existence of that thing; an act of the will is required as well to bring it to be. So it is with God; His knowledge is the cause of the being of things in conjunction with His will.

A9: God knows everything that exists, but what about things that don’t exist? In what sense can they be known anyway? Aquinas affirms that “God knows all things that are in any way whatever”, but then has to explain how we can talk about the non-existence of things. If we think about unicorns then we can say that they do not exist as concrete particulars in the world, but they still have some sort of existence in our minds or we could not even talk about them. Aquinas’s solution follows this line of thought. God knows everything that exists and everything that can potentially exist. These things all exist in His intellect; they come to be by the single act of His will. However, a distinction is made between different sorts of non-existence: we can consider things that currently don’t exist but which have existed in the past or will exist in the future. God is in eternity with His “present” gaze directed to the whole of time so He can “see” these sorts of (currently for us) non-existing things in their proper time. God knows these sorts of things through what is called “knowledge of vision”. But He can also know those things that currently don’t exist, never have existed, and never will exist! These things only ever exist in potentiality, but it is a potentiality that God knows through His “knowledge of simple understanding”.

A10: Does God know evils? Since He knows everything, surely He must know evils as part of everything. But God’s knowledge is creative, so does God therefore create evil? Evil is a privation of the good and therefore in potentiality to its corresponding good; but God is pure actuality, how can a potentiality be part of His substance via His knowledge? Aquinas turns these tricky questions around by asserting that perfect knowledge involves knowing the balance between potentiality and actuality in things and in knowing its being as far as it is in being. Therefore God must know evils through knowing the degree to which things are. So God’s causative knowledge does not cause the evil of a thing but causes the goodness of the thing insofar as it is good. Similarly, possessing knowledge of a potentiality is not the same as having a potentiality in the intellect; rather it reflects complete knowledge of the thing known.

A11: Aquinas has already dealt (in article 6) with God’s specific knowledge of things. Now he takes the argument one step further; He knows each individual thing as an individual. Again, this may seem a curious question, but Aquinas is concerned to refute incorrect understandings of knowledge. The objections to this article focus on the proposition that since God is totally free of matter and since matter is the principle of individuation of any thing, God cannot know things inasmuch as they are individuated by matter. God is, so to speak, far removed from the realm of the individual and His knowledge is confined to the universal. Aquinas points out that certain attempts to get over these objections by suggesting that God knows individuals through universal causes don’t work. He answers that since our knowledge of individuals is part of our perfection and all perfections of creatures exist in God, God must know individuals too. Building on the answer to article 8, Aquinas argues that since God’s knowledge is causal, His knowledge must extend to all the factors that make individuals individual, or else He couldn’t cause them.

A12: Aquinas now asks whether God can know infinities. This might be rather tricky as we’ve already seen that he takes the view that although we can conceive of unlimited things, actual completed infinities do not exist. How then can God know them? Since God knows not only that which is but also that which is not, and the latter is infinite, He must know infinities. We might think that Aquinas may retreat to the assertion that God knows infinities through his “knowledge of simple understanding” that we met in article 9; but he doesn’t. Aquinas actually asserts that God knows infinities through His “knowledge of vision”, i.e. as laid out before Him as he surveys all of created time from the vantage point of eternity. This is because God knows the infinite number of actual and potential thoughts that all rational creatures have. The reason that God knows these infinities is that God knows every aspect of every individual (as we have seen in article 11) and that knowledge is creative (for all that is or can be). In the answers to the first two objections, Aquinas suggests that although we have to go through unlimited potential infinities part by part, not able to know them as an infinite whole, God can grasp their whole infinity in one go. However, his answer to the third objection suggests that even God cannot “quantify” an infinite set. I suspect that if Aquinas had a modern understanding of infinite sets, he would alter his answer to this objection and allow God to quantify infinite sets in His act of knowing.

A13: A future contingent event is an event in our future that is neither necessarily true nor necessarily false. Does God know future contingents? It might seem that He does not because God causes all things that He knows and it’s hard to see how His causative knowledge can be anything other than necessary. Similarly, if God knows everything that is in one act of knowing that traverses all of our time, how could it be that everything that is going to be could be anything other than determined (and therefore not contingent)? These questions are among the most intractable in philosophical theology (and apply to any religion in which there is a sufficiently “powerful” God). Aquinas’s answer is disarmingly simple: God knows all things; some things are future contingent (our acts of free will, for example); therefore God knows future contingents. He elaborates his basic answer by observing that we can consider future events contingent in different ways: these basically correspond to God’s way of seeing them as immediately present to Him; and to our way of seeing them as contingent through causes not determined to a particular outcome. Aquinas’s point of view appears to boil down to saying that the kind of knowledge that God has is sufficiently different to our knowledge that it is consistent to say that God can know something as determined whilst it can be contingent to our knowledge.

A14: A “proposition” as far as Aquinas is concerned is a sentence affirming or denying a predicate of a subject. Propositions are abstract in the sense that they are independent of the language in which they are expressed. Does God’s knowledge include propositional knowledge? It might be argued that constructing propositions to express facts is something special to the way that humans think. We think of a subject and of the predicates associated with it and construct propositions to express these relationships; a very linear and methodical way of thinking. Surely God’s knowledge is above this rather plodding way of doing things? However, since God knows everything about every individual, He must know the propositions that each individual forms. However, God’s knowledge of these propositions is not like ours; He knows everything in one act of knowing and does not have to plod through the process of putting propositions together. He knows these things through the essence of their truth or falsehood, abstracted from their means of expression.

A15: In the created world things proceed with the flow of time, changing this way and that. God knows all of these changes, so it would seem that His knowledge must therefore change. Not so, God is unchangeable (Ia 9.1) and His substance is His knowledge (article 4), so His knowledge is unchanging. The answers to the objections follow the same pattern as given in Q9 where Aquinas considered the relations between creatures existing in time with God existing in eternity; relations can change whilst one of the parties within the relation remains unchanged.

A16: In his commentary on Aristotle’s Metaphysics, Aquinas wrote that “the end of theoretical knowledge is truth, whereas that of practical knowledge is action”. He inherits the idea that knowledge can be divided into these categories of theoretical and practical and he asks here which category God’s knowledge falls into. As he has already shown that God’s knowledge is causative, we might think that His knowledge is therefore practical. Conversely, Aristotle claimed that theoretical knowledge is more excellent than practical knowledge; therefore God’s knowledge must be theoretical. Aquinas argues that God’s knowledge of Himself must be theoretical as there is no sense in which He (who is pure actuality) can be produced any further. But His knowledge of everything created is both practical and theoretical as He knows all things both from the point of view of what they are in themselves and form the point of view of bringing them to be.

Handy Concepts

  • The “agent intellect” organises and assimilates the information received from the senses (so it is the “active” part of the intellect) and the “passive intellect” receives and keeps the intelligible species offered to it by the agent intellect.
  • “Intelligible species” are the immaterial forms of things that our intellect grasps in order to understand them.
  • The “knowledge of approbation” is God’s knowledge of things considered as their cause.
  • God’s “knowledge of vision” applies to things that although they do not exist now, either have existed or will exist in the future. God’s “knowledge of simple understanding” applies to things that do not exist, never have existed and never will exist.
  • A future contingent event is an event in our future that is neither necessarily true nor necessarily false.
  • A “proposition” is a sentence affirming or denying a predicate of a subject.


  • We pointed out that article 11 raises problems in philosophical theology that are very difficult. For example, actions that are the result of our free will are future contingent (before the actions are placed). If God has knowledge of vision of such events how can they really be considered as free choices (as opposed to determined)? In particular, how can our free choice to turn to the Lord (or not) truly be considered free?
  • In article 12, it appears that Aquinas’s concept of infinity makes him reach conclusions that he might reconsider in the light of modern knowledge of the infinite.

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