The Aquinas Papers: God Is Eternal

Abstract: Thomas Aquinas purposed to demonstrate the inter-relatedness of God’s attributes insofar as when we predicate something of God, viz., eternality, then we say more than, “God is eternal.” Rather, for Aquinas, if God is eternal, He must also be necessary, pure act, and divinely simple––other things follow as well. Yet, for Aquinas, our language is not univocally representative of who God is in Himself, but analogical; this will be explained in later installments. In this paper, I work to exposit Aquinas’ view of God’s eternality or timelessness in contradistinction to modern philosophers, like Dr. William Lane Craig. In doing so, I will prepare the reader for the following paper in the series, which will demonstrate Aquinas’ view of God insomuch as, in God there is no passive potency.

It is not uncommon for non-Christians and Christians alike to posit eternality of God. It is basically assumed in the use of the term God; we mean to indicate a Being higher than all other beings. The church, both in the Old and New Covenants, has bore witness to this fundamental truth about deity. Therefore, when someone like Thomas Aquinas––a medieval-era Catholic priest and scholar––writes about God’s eternity, it shouldn’t surprise anyone. Yet, we would do well to pay attention to Thomas’ particular construal of such a doctrine because, being a precise thinker, he is concerned to cohere the church’s theology of God into one rational whole which maintains internal consistency, more so, I would argue, than any contemporary thinker.

However, in our day and age of theological whim, this coherence has been lost among large swaths of Roman Catholic, Eastern Orthodox, and Protestant populations. We may hold to the eternality of God without understanding a single iota of the doctrine itself, let alone its correlates. Thus, it is necessary to recover some of the precise distinctions made by Thomas so we can maintain a doctrinal integrity within the church.

Aquinas’ doctrine of God flows from that which can be understood of God via rational inquiry. For example, in the Summa Contra Gentiles (SCG), Thomas argues (a la., Aristotle) for the existence of God from motion.[1] The God concluded as a result of the argumentation is an eternal God. This is because a first unmoved mover must be eternal since, to begin to be or to begin to not-be in the future is to be moved from one state of being to non-being. Aquinas says:

Everything that begins to be or ceases to be does so through motion or change. Since, however, we have shown that God is absolutely immutable, He is eternal, lacking all beginning or end.[2]

A necessary application, therefore, of God’s immutability is to also see God as eternal. Without one, the other cannot be. It is also helpful to note how Thomas sees time, fundamentally, as a measurement of change. Thus, for God to change would render Him in time. Conversely, for God to be in time, that is, measured by it, would be for God to change. Thus, logically, God is eternal, and we proceed to this conclusion because we first know that God is unchanging. He goes on:

What is more, if it were true that there was a time when He existed after not existing, then He must have been brought by someone from non-being to being. Not by Himself, since what does not exist cannot act. If by another, then this other is prior to God. But we have shown that God is the first cause. Hence, He did not begin to be, nor consequently will He cease to be, for that which has been everlastingly has the power to be everlastingly. God is, therefore, eternal.[3]

If God is the first cause, then there can be nothing behind God causing God to be. Otherwise, whatever is behind “God” causing “God” to be “God” would, in all actuality, be God. There is a more nuanced application of Thomas’ words yet to be exposed. If God is said to be in time, which is the case in much of today’s theology, and if time is a measurement of change, then God is in process. But if God cannot be measured, because immutable, then it cannot be logically stated that God is in time. However, the rational implication of stating that God is in time is to hold a version of process theology where God is in a state of becoming rather than pure Being.

In the next paper, we will concern ourselves with Thomas’ contention that there is no passive potency in God.[4] In that paper, we will examine how Thomas deals with the implications of putting God in time, which would be to predicate passive potency in God. If there is no passive potency in God, then there is no sense in which God could at one point be outside of time and then at another point, measured by time. Moreover, if there is no passive potency in God, there can be no process of becoming in God. Therefore, God cannot be measured by time, which means that God cannot properly be said to be in time. Contemporary philosophers, like Dr. William Lane Craig, competes with Thomas’ view by saying:

Imagine God existing once more, alone, without the world, without the creation. Now in such a state, God is either timeless or temporal. If He’s temporal, then the issue is decided. God is in time. So let’s suppose that He’s timeless. And now let’s suppose that God decides to create the world, and He brings the universe into being. Now when He does so, God either remains timeless or else He becomes temporal in virtue of his new relationship to a changing world. If God becomes temporal, then clearly He is in time. So could God remain timeless while creating the universe? Well, I don’t think so. Why? Because in creating the universe God undergoes at least an extrinsic change—a relational change. At the moment of creation He comes into a new relation in which he did not stand before because there was no “before.” It’s the first moment of time. And at the first moment of time, He comes into this new relation of sustaining the universe or at least of co-existing with the universe, a relation in which He did not stand before. And thus, in virtue of this extrinsic, relational change, God would be brought into time at the moment of creation.[5]

Craig makes a distinction between intrinsic and extrinsic change. We might, on the face of it, conclude Craig is referring to the ad intra/ad extra distinction; but he means something altogether different. When we refer to God ad intra we mean to indicate something of what God is in Himself. When we discuss God in ad extra terms, we mean to speak of God as we experience Him through His revelation. Craig, on the other hand, with his intrinsic/extrinsic distinction is really talking about change in God via internal and/or external mutation. For Craig, change external to God causes God to change extrinsically. So, God is not changing intrinsically, but He is changing extrinsically. This is really a distinction without a difference upon final analysis. First, it does not follow that since something changes outside God that God, therefore, changes. Rather, we change in relation to God. At best, there may be what we might call a Cambridge change in relation to God which is, itself, not a real change in God but only the change of something else in its relationship to God. It appears Craig actually refers to a Cambridge change, not any real change, when he discusses God changing in relation to His creation. And that would be to say that God does not change, but creation changes in relation to God. Second, an extrinsic change would result in an intrinsic, or essential, change in God. Otherwise, it could not be said of God that He changes. If God doesn’t change in essence, then He changes not at all. If God changes, then His essence changes. The reason contingent objects may change extrinsically, that is, in relation to another thing, is because they are measured by time in relation to things around them. So, to say God changes, even extrinsically, when trying to demonstrate a kind of temporality in God is to assume what one is trying to prove––that God is temporal in some sense. But this violates the petitio principii fallacy. Third, because there is no passive potency in God, but only active potency, creation cannot change God simply because creation itself changes. Nothing that occurs outside of God can change God because that would be to implicitly predicate passive potency in God. But, the discussion on God’s lack of passive potency will be at the forefront of the following paper––being the very next issue Thomas deals with after eternity.

In the same place, Craig goes on to discuss God’s knowledge of tensed facts. He says, “Now notice that I, in virtue of knowing tensed facts, must have a temporal location. If I know today is July 20, then I am located at July 20.”[6] If God, it is thought, knows tensed facts (e.g. today is St. Patrick’s Day), then God must have some sort of temporal location. But this does not follow for a few reasons: First, if God is eternal by nature, His knowledge is pure act. That is, His knowledge undergoes no succession and it, therefore, is not ratiocinative or discursive knowledge. Second, tensed facts are only located, so to speak, in creation––that is, within time. God does not know facts in a tensed manner. In fact, if God’s knowledge is pure act, then it can’t know discursively and so, “Today is my birthday,” is a fact God knows from eternity or, we could say, a fact eternally present to God. Speaking of God’s knowledge of things that do not yet exist (or may never exist), Aquinas says:

Hence, whatever is found in any part of time co-exists with what is eternal as being present to it, although with respect to some other time it be past or future. Something can be present to what is eternal only by being present to the whole of it, since the eternal does not have the duration of succession. The divine intellect, therefore, sees in the whole of its eternity, as being present to it, whatever takes place through the whole course of time. And yet what takes place in a certain part of time was not always existent. It remains, therefore, that God has a knowledge of those things that according to the march of time do not yet exist.[7]

From this, we glean that God knows with an eternal knowledge. Therefore, all facts must be present to Him. According to Craig, however, a tensed fact places God in some temporal location. However, the argument for God’s temporality only tends toward this conclusion because it assumes the very thing it is trying to prove. For God to be temporally located, and for God to know in a tensed manner, God would have to be temporal! But God is not temporal; He is eternal and must be eternal if the classical arguments for God’s existence are consistently applied, as shown in the earliest chapters of Thomas’ SCG, Vol. 1. In summary of this point, God knows tensed truths in a tenseless manner in that all God’s knowledge is eternally present, being a most pure and eternal act.


Aquinas deals with eternity in a way that is rationally coherent and in line, logically, with other doctrines concerning the God of the Bible. Aquinas’ view of eternity, along with some of its implications, has been vividly discussed and even compared to a major contemporary view. It has been demonstrated that to posit change in God is to put God in time and is, therefore, to rip God’s eternity from Him.


[1] Aquinas, Thomas. Summa Contra Gentiles. Vol. 1, (University of Notre Dame Press, 1955), 85.
[2] Ibid., 98.
[3] Ibid.
[4] Ibid., 100.
[5] Craig, William L. “God, Time, and Eternity.” Reasonable Faith, www.reasonablefaith.org/writings/popular-writings/existence-nature-of-god/god-time-and-eternity1/.
[6] Ibid.
[7] Aquinas, Thomas. Summa Contra Gentiles. Vol. 1, (University of Notre Dame Press, 1955), 219.

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