While the question of God’s existence is an important one, this is only one side of the objective/subjective coin. That is, we have asked the (objective) metaphysical question “Does God exist?” but for this post we are flipping to the (subjective) epistemologicalquestion, “How do we know God?” Thomas Aquinas categorizes these levels of questions three-fold: (1) What God is (or “is not”), (2) how God is known by us, and (3) how we can express that knowledge.
In a brief section of the Summa after he had established his case for the existence of God, Aquinas writes:
When the existence of a thing has been ascertained, there remains the further question of the manner of its existence, in order that we may know its essence. Now. . . we cannot know what God is but rather what He is not. . . therefore we must consider, first, how He is not, second, how He is known by us, and third, how He is named.
In this post, questions (1) and (3), important as they may be, will not be addressed here. However, to be clear of question (2), I do mean a philosophical or natural knowledge of God. Christians may have a knowledge of God by Scripture or divine revelation, but the knowledge I have in mind here pertains to what knowledge we might able to obtain virtue of our natural reason. Aquinas offers us four metaphysical principles as the basis of our natural knowledge of God. They are as follows:
As Peter Kreeft nicely put it, if God created the universe, then that would entail that there is some relation between God and the universe. Since there is a relation between God and the universe, there is therefore a possibility of a relationship between God and man.
Given how Aquinas understood cause and effect*, we can inquire (or infer) into the cause (God) from the basis of the effect (creation). While this knowledge of God is highly limited, we can at least say two things here: (a) from the basis of this cause and effect relationship we cannot have a “perfect knowledge” of God, but (b) we can nonetheless demonstrate the existence of God from this basis although we cannot know the “manner of existence” (or essence) of God.
Don’t let me mislead you, (b) is really just an of (a). However, the claims are quite different. Aquinas had said that “[f]rom effects not proportionate to the cause no perfect knowledge of the cause can be obtained.” That is, given the (wide) disproportionality between God and creation, we cannot step into “perfect knowledge” of God. Second, according to (b), even though this is the case, this cause and effect disproportionality nonetheless still allows us to know whether or not God exists (by way of demonstration).
As seen from Aquinas’ Fourth Way, we notice that from the gradation that occurs in things, such as things “found to be more good, true, noble and so on, just as others are found to be less so,” we can argue to the existence of God.
More specifically, things can be organized by their degrees of perfection (or “gradation of being”). From these degrees of perfection, Aquinas was able to argue that “[t]here is. . . something which is the truest, the best, and the noblest, and which is consequently the greatest in being.” However, Aquinas by this metaphysical principle meant something more than an exercise in our natural reason to make a case for God’s existence.
Apart from divine power to bring about creation, there is also divine intelligence. That is, there is order, or design, in the universe. This is a way of saying that God has created a kind of “cosmic hierarchy,” or a “great chain of being.”
Analogy of Being
This is something a number of people tend to trip up with, mainly due to the language Aquinas used. To be clear on a couple things: (1) the previously discussed metaphysical principle is implicit within Aquinas’ understanding of analogy and (2) this is further rooted in his understanding of causality.
Analogy at its core maintains that the judgements (predications) we make of God are analogous only in the manner used between God and creatures. For example, we can say that both God and humankind are good. However, when we ascribe the predication of good to God we must do so infinitely, while with humankind we may only do so finitely. As Aquinas has put it, “all perfections exist in creatures dividedly and. . . in God unitedly.” In other words, we cannot apply characteristics to God and humankind and mean them in the same way. We can, however, say that they are similar (i.e., analogous).
Furthermore, how is causality related to analogy? Since God is “Pure Existence” (or Actuality) and since he causes all other existence, “there must be a similarity between him as the Efficient Cause and his effects” (Geisler 1991, 129). In other words, what can be said of God and creatures (as Aquinas stated) “is said according as there is some relation of the creature to God as to its principal cause.”
Lastly, and stated in a phrase, human reason is able to participate in divine reason. Since man was created in the image of God, he is able to participate as well as reflect divine reason by virtue of man’s three kinds of “reasoning”: (1) understanding, (2) judging and (3) reasoning.
That is to say, that while the relation between God and creatures is analogous, it is by no means passively so. God is of course not some blind, cosmic force sitting behind the desk of the universe with his divine keyboard before Him. He is personal and intelligent. Godhas a mind. This again, turns us back to analogy. We are not only able to resemble our cause by analogy (third metaphysical principle) but we, as creation (effect), are also able to participate in the power of the cause (first metaphysical principle).
Geisler, Norman. Thomas Aquinas: An Evangelical Appraisal. 1991. Eugene, OR: Wipf and Stock,
*Aquinas maintained that the activity of a cause (that is, if it is a cause) expresses itself in the existence of an effect. For example, a modern may look at change and causality as the cause A who brings about the effect B, B then brings about C, and so on. Aquinas would have said that it is the change in the effect B as seen from the cause A. See my article on Aquinas’ cosmological argument (as I have linked) for a more extended discussion.