Eternity’s relation to time

A few months ago, reader Ante asked this question on my What I Believe page:

I am very much struggling how to combine a presentist account of time (like the A-theory for example) and the view that God is outside of time, in a Thomistic sense.

I would be very thankful for your help, since it seems to me that I am hitting a wall regarding this issue, since I cannot accept a B-theory of time, but at the same time the view of St. Thomas regarding God’s eternity is much more plausible than the other philosophical alternatives (especially open theism!).

For those unfamiliar with the relevant terms, we begin by briefly explaining what the A-theory and B-theory are, how they relate to presentism, and what this has to do with God’s eternity.

The distinction between A- and B-theory of time was introduced to analytic philosophy by McTaggart in his paper The Unreality of Time. Briefly, the A-theory of time holds that there is some objectively privileged moment of time we call the present, relative to which other moments of time can be categorized into past and future (called the A-series). By saying it is objectively privileged we mean that the fact of which moment is present is not a matter of perspective, but is rather a feature of reality prior to any considerations from us. The B-theory, by contrast, denies that there is such an objectively privileged moment of time, and holds that the only relations between moments are those of earlier than and later than (called the B-series). We can still speak of the present, but it must always be understood from the perspective of a particular moment under consideration. The most we can say, for instance, is that from the perspective of the 3rd of March 2018, the 2nd of March is in the past and the 4th is in the future.

Each of these theories has a number of models, which are concrete proposals for the nature of time that satisfy the requirements of the theory. Confusingly, these models are also sometimes called “theories.” A-theoretic models include presentism, which holds that only the present moment of time is real, while the past moments were once real and the future moments have not yet become real; the spotlight theory, which holds that all moments of time are equally real but only one ever has the property of “presentness”, which leads to us visualizing time as a spotlight gradually moving over a fixed timeline; and the growing block theory, which holds that once a moment is real is stays real, resulting in all past moments being equally real and forming a “block” of time, with the present being on the edge of this ever-growing block. B-theoretic models include four-dimensionalism, which treats time like a sort of spatial dimension, holding that objects have temporal parts spread across the fourth dimension of time just like they have spatial parts spread across the first three dimensions of space; and eternalism, which we will here take to be the model that all moments of time are equally real without any having the status of being objectively present, but not necessarily construed as temporal parts of objects either.

As for God’s eternity, the Thomistic view is that eternity and time represent fundamentally different modes of being. Eternity is not merely about existing without beginning or end, since this would be consistent with existing in time as long as we stipulate that (1) either time itself has no beginning or end or (2) God entered time upon creation.1 The Thomistic view can be seen as a consequence of Boethius’ definition of eternity, which says that it is “the complete possession, all at once, of illimitable life.” Such an existence is incompatible with being in time, since temporal existence requires that we have our life bit by bit rather than having all of it at once. Accordingly, God’s eternity means that he must be outside of time, and the problem of eternity has to do with the relationship between an eternal God and his temporal creation.

Thomistic and analytic approaches to time

Now, for us Thomists who are familiar with the analytic distinction between A- and B-theory, it is natural to wonder how it applies to God’s eternity and his relation to time. What is not always realized, however, is that there is an important difference between the Thomistic and analytic approaches to questions of time. The Thomistic approach is Aristotelian, and therefore starts with an analysis of change. Aristotle starts by asking questions like whether change is possible and what it consists in, and considers examples like that of a person becoming educated and an object moving location. By contrast, the analytic approach — by which I mean the approach of those in the analytic tradition broadly following McTaggart — starts with the ontology of the passage of time. The main point at issue in the debate over A- and B-theory is whether the passage of time “flows” from past to future. On the A-theory it flows as the present moves from moment to moment, while on the B-theory it is in some sense static.

We saw the analytic approach in action during our discussion on McTaggart’s paper, wherein he switches between questions about changes to reality (which is change in the everyday sense of the word) and questions about changes to the time series, as if these were interchangeable. On the Thomistic approach, time is just the measure of change,2 and it makes little sense to speak of the time series itself changing, as if this could be decoupled from the change to reality which it measures. Indeed, from a Thomistic perspective the analytic approach can seem to treat time as a sort of quasi-substance, which is certainly the impression one gets from McTaggart’s talk of moments of time merging into one another or changing properties.

We can illustrate the difference between the two approaches by considering how they would attempt to answer the question of whether temporal becoming is an objective feature of reality.

For the Thomist, temporal becoming is the feature of things when they change, as when an uneducated person becomes educated or a physical object moves from one place to another. Every change involves a coming-to-be of what was not before, and in this case the becoming is of things and in time. Given this sense of temporal becoming, we can determine whether it is an objective by determining whether change is real. And since change is evident to our experience, all we need is an account of it that shows its possibility, and therefore that our experience of it need not be an illusion.

On the analytic approach, things are less clear, because temporal becoming sometimes takes on a different sense and because the two senses are not always clearly distinguished. It’s difficult to avoid talking about changes to everyday things like people and physical objects, but with a primary concern for the ontology of time this talk gets mixed up with talk about changes to the passage of time itself.3 We are no longer simply interested in whether someone who is uneducated can become educated in the future, but also whether that future moment itself is something that can become present. This is not simply a becoming in time, but a becoming of time itself. The result is the conflation of temporal becoming with the A-theory, since only the A-theory involves the passage of time being in flux. Given this sense of temporal becoming, in order to determine whether it is objective we need to determine whether the A-theory is true, and that our experience of the passage of time itself (which is much less evident than our experience of change) is not an illusion.

So these two approaches give us two senses of the notion of temporal becoming, namely becoming in time and becoming of time. The former arises from considerations of change in the Aristotelian sense, as when an uneducated person becomes educated, and a physical object changes place. The latter arises from considerations of how the moments of time itself might change, as when a future moment takes on “presentness.”

The compatibility of (Aristotelian) change with B-theory, and its irrelevance

The upshot of all of this is that the analytic debate over theories of time is irrelevant to Aristotelian and Thomistic concerns. Both A-theorists and B-theorists recognize the reality of time with its peculiar feature of being ordered according to before and after, which is all the Aristotelian needs. As Aquinas said, “time is nothing else than the reckoning of before and after in movement” (ST I Q53 A3 corp).

Failure to recognize the different senses of temporal becoming has led some to conflate views they shouldn’t.4 The B-theory, for instance, is sometimes labeled “Parmenidean,” as if these two views are even remotely similar. Parmenides denied the existence of any distinctions in reality whatsoever, which leads to the denial of change and therefore the denial of any meaningful distinction between before and after. But the B-theory presupposes a distinction between before and after, since this is built into the relations earlier-than and later-than.

Another claim is that the B-theory excludes the possibility of change, and is therefore at odds with the Aristotelian commitment to its reality. Why does the B-theory preclude change? Well, the argument goes, if all moments of time are equally real, then the earlier moments when someone is uneducated are equally as real as the later moments when they are educated, and so they never become educated. But this clearly equivocates the two sense of becoming we’ve been discussing. The Aristotelian concern is whether someone who is uneducated at some time t1 can become educated by some later time t2, not whether t1 and t2 can somehow change their properties of “presentness.” All the Aristotelian needs is that a person can persist through time while varying in their educatedness, which the B-theory happily provides. What the B-theory does not provide — but which is irrelevant to the Aristotelian — is that this happens together with a change to the moments of time themselves. Again, the Aristotelian is concerned with becoming in time, not becoming of time.

Once we recognize the difference between Aristotelian temporal becoming and analytic temporal becoming, we can see that Thomists can happily hold to either the A- or B-theory. The analytic debate just isn’t something we have a stake in. But here’s the kicker: this doesn’t help us in any way with the problem of eternity! It is tempting to think that the B-theory would give us an automatic explanation of the relationship between the eternal God and his temporal creation, but it doesn’t. Why? Because at the end of the day, the B-theory is still a theory about time.

Let me explain.

We’ve said that time is the reckoning of before and after in the process of change, but what we haven’t mentioned is that before and after can be reckoned to something on account of a change to something else. This is an instance of what’s been called “Cambridge change,” which Feser describes as follows:

Here, building on a distinction famously made by Peter Geach, we need to differentiate between real properties and mere “Cambridge properties.” For example, for Socrates to grow hair is a real change in him, the acquisition by him of a real property. But for Socrates to become shorter than Plato, not because Socrates’ height has changed but only because Plato has grown taller, is not a real change in Socrates but what Geach called a mere “Cambridge change,” and therefore involves the acquisition of a mere “Cambridge property.”

There’s a certain ambiguity in this that we’ll discuss later, but for now consider the example he gives. Socrates remains the same height while Plato grows, and on account of this we can reckon before and after for Socrates: before he was taller than Plato and afterwards he was shorter than Plato. Thus, there’s a sense in which the change of other things can bring us along with them through time. Since this results from our being able to reckon before and after through changes to things in time, and since both the A- and the B-theory give us this, this will apply on both theories.

The real problem of God’s eternity, then, isn’t about whether the nature of time is such that all moments are equally real, but about how our movement through time doesn’t bring God along with us. And since this happens for both A- and B-theories of time, neither of them is capable of solving the problem.

Starting over with relations

Rather than a theory of time, what we need is a theory of relations. The reason Plato brings Socrates along with him through time is that Socrates is really related to Plato in some respect. In the above example it is that they are really related in regards to their height, but it could equally have been their relative location, color, age, or whatever. Conversely, if Socrates were not really related to Plato with respect to some feature of Plato that changes, then there would be no way of reckoning before and after for Socrates in terms of a change in Plato.

Aquinas worked out a detailed theory of relations, and we will summarize the relevant parts here. First, relations are divided into real relations, which obtain in reality prior to any consideration by an intellect, and logical relations, which result from such consideration. Socrates being taller than Plato is a real relation, but Socrates being to the left of Plato is logical since it is dependent upon how one considers their relative positions. When something has a real relation to another thing we say that it is “really related” to it. In English, the word “really” is often used to mean “truly” — as when we say something “really happened” — but in our present case “really” just indicates the nature of the relation. Socrates being to the left of Plato is not a real relation, but it is nevertheless true that Socrates is to the left of Plato.

Now, a relation between two things is not some separate reality floating outside of those things, but is instead grounded in them. When we have some relation R between A and B, it is therefore technically more precise to speak of R as a pair of relations, R1 from A to B and R2 from B to A. Socrates is taller than Plato (R1) and Plato is shorter than Socrates (R2). Each relation has a foundation in the thing it relates from, and this foundation grounds how that thing relates to others. For instance, Socrates has a certain height H, by virtue of which he will be shorter than things with heights taller than H and taller than things with heights shorter than H. This generic relational fact comes to be “resolved” to one of the alternatives when considered with respect to a particular individual: Plato has a height shorter than H, and so Socrates is taller than Plato. Notice that since the relation from Socrates to Plato will depend on both their heights it can change without Socrates ever changing, as when Plato changes his height while Socrates remains the same. It is this change in the relation from Socrates to Plato that brings Socrates through time when Plato changes.

We can also talk about the type of relation, which is derived from the type of its foundation: the taller-than relation is based on height while the brighter-than relation is based on color. In addition to the foundation in A, a real relation from A to B requires something in B of the relevant type, which we might call the relation’s co-foundation. It makes little sense, for instance, to say that Socrates is taller or shorter than an immaterial angel, since a relation of height from Socrates to another thing requires that that thing have a height as well. There is no co-foundation of the relevant type in the angel.

We say that the co-foundation must be of a “relevant” type rather than the “same” type because sameness is not always required. The height relation is an example that requires the co-foundation to be the same type, but consider what happens when I come to know a material object. In this case I take on its form in my mind, which serves as the foundation for a real relation from me to it and which has the object’s own form in itself as the co-foundation. But these two forms have different types: the form in my mind is intentional while the form in the object is entitative; the form in my mind does not turn my mind into that object whereas the form in the object’s matter does.

Knowledge is also an example of what is called a non-mutual relation. We have said that my real relation to the object has its foundation in the intentional form in my mind and its co-foundation in the entitative form in the object. This works because of the intentional form by its very nature refers to the object of the intention. But the entitative form is about constitution rather than reference, and so does not refer back to the intentional form in my mind. It can serve as the foundation of relations to other things by comparison to their entitative forms, but that’s about it. This means that there is no corresponding real relation from the object to me that has its entitative form as foundation and the intentional form in my mind as co-foundation. This asymmetry in foundation and co-foundation is what makes the relation non-mutual. When a real relation from A to B is can be turned into a real relation from B to A simply by flipping the foundation and co-foundation, then that relation is mutual.

If this were not complicated enough, consider what happens with active and passive powers. Here we have an agent with an active power (ability to influence others) and a patient with a passive power (capacity to be influenced by others), and when the agent actually does influence the patient then we have action and passion. The active power of an agent is grounded in some actuality (actual feature) of the agent, like motion, size, intentions, and so on. Any relation that arises from the active power, then, will have this ground as its foundation, which will determine which co-foundations are relevant. The passive power of a patient is slightly different in that it is grounded in the potential of the patient to be influenced in a particular way. This potential will be the foundation of the relations that arise from the passive power, and the co-foundations will be any actuality that can actualize it.

There is an important asymmetry here, in that the conditions for an agent to really relate to the patient are different from the conditions of the patient to really relate to the agent. For a patient, all that is needed is something capable of actualizing it, but for the agent, the conditions will depend on the ground of the active power. It could happen, then, that a patient is really related to an agent by a non-mutual relation. Consider, for instance, a saw cutting through wood. We might say that the active power of the saw is grounded in the sharpness of its serrated blade, while the passive power of the wood has to do with its potentiality for being split. Certainly there is a real relation from the wood to the saw because of this passive power, but as for the active power the wood is not really comparable in terms of sharpness or serratedness. The wood is really related to the saw, then, with a non-mutual relation. Of course there are other real relations between the two that have to do with active and passive powers and which are mutual. The saw might be used to push the piece of wood, for instance, in which case the ground of the active power (the motion of the saw) has a relevant co-foundation in the wood (the motion of the wood).

The problem of eternity

With this we can state the Thomistic answer to the problem of eternity: God is not really related to creation, and is therefore not brought through time by our changes.

This arises from applying what we’ve said about relations to the nature of God. For Thomists, God is a being of pure actuality, with no potentiality in him whatsoever. This makes him radically unlike anything else in reality, all other things being made up of a combination of potentiality and actuality. Furthermore, since potentiality is what allows for the diversity of actuality within a thing, it follows that God’s purely actual substance is the only possible foundation for real relations from him to others. But since pure actuality is so different to anything else in existence, it follows that there can be no relevant co-foundation to this purely actual foundation, and that therefore God cannot be really related to anything else.

Creation is still really related to God, mind you, but this relation is non-mutual. We are really related to God by virtue of our dependence on him for our being, and by virtue of being ordered toward him as the ultimate final end (cf. ST I Q44). Both of these arise from us being patients of God’s activity, and it is because of the potentialities in us that we can be really related to him — although pure actuality might be very different from us, it is nevertheless capable of actualizing all the potentials in us. Conversely, since God has no potentiality in himself there can be no chance of him really relating to us by virtue of us acting on him in some way.

Not only does God’s pure actuality exclude real relations from him to us or our acting on him, but it also excludes the possibility of change within him. All change involves the actualization of a potential, after all, and so without a potential there is no possibility of change. This notwithstanding, he is the source of all actualizations of potentials, including all instances of change. Thus God is called the Unmoved Mover, or Unchanged Changer, or more generally the Unactualized Actualizer. It might sound a bit strange to say that something could cause change without itself changing, since in our experience these tend to coincide. But it is a consequence of the fact that action and passion arise by an actuality of an agent actualizing a potential of a patient.5 This does not require that the agent’s actuality itself be the actualization of a potential, even if that happens with all the material agents we experience in the world.

Now, we might wonder why God would not be really related to us by virtue of knowing us. God is omniscient, after all, and earlier we mentioned that a knower is really related to the object of their knowledge. Here we must again appreciate the difference between God and ourselves. We come to know things outside ourselves through inquiry and exploration, by means of which we acquire the intentional version of its form in our mind. The entitative form in the object stands as a measure to our conception of it, and it is to the extent that our conception fulfills this measure that it is said to be true or accurate. With God, things look very different. His act of knowing reality is the same act whereby he creates and sustains everything in reality, and so he has no need of inquiry or exploration. He does not discover anything and has no need to acquire new knowledge by means of taking on the intentional forms of things. Since it is by his activity that all things continue to have their being, and since his act of knowing is the same as this activity, it also follows that God’s knowledge is measure of things rather than the other way around. All of this means that God’s knowledge does not make him really related to us like our knowledge makes us really related to the objects of our knowledge.

So, God does not change and is not really related to things that change. This means that there is no way of reckoning before and after for him and that therefore he is not in time. This notwithstanding, he is still the creator and sustainer of everything, and by virtue of this we are really related to him. Just as God is an unchanged changer, so too is he the non-temporal cause of things in time. We must remember, of course, that being really related to something is not the same as being truly related to it. Despite not being really related to us, God is still truly related to us as Lord, Creator, Knower, and so on; it’s just that these true relations are based on logical relations from him to us rather than mutual real relations between him and us.

Now before we conclude, we said earlier that there is an ambiguity in the notion of Cambridge change, and we are finally in a position to see why. Sometimes Cambridge change is proposed as a solution to the problem of God’s eternity, but of itself this is insufficient. To say that God only undergoes Cambridge change is to say that he does not undergo any change within himself. This is fine so far as it goes, but it doesn’t explain why he isn’t brought through time by changes to other things — as we saw in the example of Plato and Socrates we used to introduce Cambridge change. This further step requires the approach we’ve outlined in this post. The upshot of this is that either we should say (1) that God doesn’t even undergo Cambridge change, or (2) that Cambridge change must be divided into instances that bring us along through time and instances that don’t. In this second option, the two species of Cambridge change are distinguished by whether there are the relevant real relations in place or not.

Conclusion and further reading

So, Ante, thanks for the question and sorry for taking so long to reply. As I see it, the Thomistic approach to time is largely indifferent to the analytic debate over A-theory and B-theory, and the problem of eternity is not caused or solved by embracing either of these. What we need for a solution is an account of when and why things are brought through time, and an explanation for why this does not apply to God. To this end, the Thomistic account of relations provides us with a promising start. I hope what I’ve managed to outline here helps.

On the topic of relations, Mark Henninger’s Aquinas on the Ontological Status of Relations and David Svoboda’s Aquinas on Real Relation are both excellent discussions on the account of relations laid out by Aquinas. From Aquinas himself, perhaps the most important place to start is his discussion in question 7 of the De Potentia, especially articles 9–11. His discussions on God’s knowledge through his substance and the divine relations in the Summa Theologica are also noteworthy, since they push the account of relations to its limits when applying it to God.

More broadly, Edward Feser’s Classical Theism Roundup is a great resource for thinking through issues like eternity. Moreover, while I think Thomists don’t have a stake in the analytic debate between A-theory and B-theory, that is not to say that we don’t have interesting contributions to make. A case in point is Elliot Polsky’s Thomistic Special Relativity, which provides a three-dimensionalist account of length contraction and time dilation using a Thomistic framework that is different from other A-theoretic approaches I’ve seen.


  1. This is the view of William Lane Craig. See, for instance, his God, Time and Eternity. I also discussed it in my pre-Thomist days in an earlier post.
  2. Or, more accurately, it is the numbering of change according to “before” and “after”. (ST I Q10 A1 corp.) We’ve discussed before the connection a measure must have with what it measures.
  3. I’m not the only one who sees this. According to the SEP article on Being and Becoming in Modern Physics, “What emerges from the McTaggart literature is, first of all, a tendency to identify the existence of passage or temporal becoming with the existence of the A-series (that is, to think of becoming as events changing their properties of pastness, presentness or nowness, and futurity) and hence the tendency for debates about the existence of passage to focus on the merits or incoherence of the A-series rather than examining alternative accounts of becoming.” Note that the “events” mentioned in the parenthesis should be taken to mean “event-slices,” since an event in the everyday sense is something that spans multiple moments of time, and not all slices of it will be present (or past, or future) simultaneously. Again, this is a usage that we see in McTaggart’s paper.
  4. I stumbled upon a recent example of this while writing this very post.
  5. See my earlier post Lonergan on Aquinas on Causation for a discussion of this in Aquinas, as well as the essential agreement between him and Aristotle despite a terminological difference.

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