It is an article of the Christian faith that God is eternal; but what does this mean? If we think that it just means that God has been from the beginning of time and will be to the end of time, we run into the problem that this seems to put God inside of time and dependent in some way upon it. To maintain this position will eventually conclude with a fall into the error of dualism; that the God that we know and love is but a secondary God created by a higher God. Therefore it is important for Aquinas to enquire at this point into what eternity means and what it means for God to be eternal. He also introduces the idea of aeviternity, the measure of change in immaterial creatures.
The Thread of the Argument
A1: If we are going to talk about God’s eternity, we will have to understand what we mean by eternity. If we are going to understand what eternity is, we will have to approach it from our understanding of time. Aquinas argues that time is defined by reference to change; it is the “numbering of before and after in change”. The old joke puts it well: “Time is God’s way of stopping everything from happening at once”.
In contrast, the notion of eternity is derived from things in which there is never any change or any possibility of change. Aquinas is careful not to locate eternity as being somewhere, leaving the definition open to further elaboration. He is willing to connect eternity with time by saying that anything existing in eternity has no beginning or end and that eternity itself exists as an instantaneous whole, recalling Boethius’s definition that “eternity is the complete and instantaneously whole perfect possession of interminable life”.
A2: Aquinas turns to the question of whether God is eternal. The two major objections state that even if God is “in” eternity, this seems to measure or contain him; and secondly, scripture uses present, past and future tenses when talking about God. Against these objections we have the creedal teaching about God’s eternity.
In a very compact reply, Aquinas points out that God’s eternity follows straight away from the fact that He is utterly unchangeable. In fact he puts the matter more strongly claiming both that “God is his own eternity” and that “eternity and God are the same thing”. We might recall here that when we consider God’s omnipresence (Ia.q8.a2) we shouldn’t think of God as being contained within all places, but rather of God being present to all places as the efficient cause of their existence and of the cause of them having the power to be places. Similarly, when we think about eternity, we shouldn’t think of God as being “in” eternity as if eternity was something external to God that contained Him; eternity is what God is by His immutability.
The first major objection clearly falls. The answer to the second objection recognizes that we have to think about the relationship between time and eternity. When we use temporal language about God, we are recognising that, in some sense, God’s eternity contains all that is in time. We must also recall that language can be used informally, as when we talk about an unbounded extent of time as being an eternity.
A3: Having claimed that “eternity and God are the same thing”, it is not surprising that Aquinas will now claim that eternity belongs properly only to God. This follows from the conclusion of Ia.q9.a2 where Aquinas has shown that only God is truly unchangeable. Created things may receive a share of God’s eternity but it is only a share; their eternity is derivative from God’s eternity. For example, the blessed in heaven having attained their ultimate end are unchangeable; they now participate in God’s eternity.
We do observe that that scripture sometimes refers to things other than God being eternal; but this should be thought of in the light of this idea of the sharing in eternity or by noticing that the word “eternal” is amenable to informal usage. The objection that necessary truths are eternal is answered by observing that that this is because such truths exist in God’s mind, obtaining their eternity by sharing in His eternity.
A4: How are time and eternity related? The first step in understanding this relationship is to show that time and eternity are essentially different things; one cannot simply identify time as a subset of eternity, as the first objection does, since they are not measures of the same type of thing.
Aquinas observes that the fundamental difference between time and eternity is that time measures change and eternity measures permanent unchangeable existence. One must follow Boethius in recognising that eternity exists as an instantaneous whole. There is no flow of time in eternity; there is no “now” other than the entirety of eternity. Time, on the other hand, flows; this flow of time consists in the changing “now” that refers to the changing or changeable things that time measures. One might wish, as in the second objection, to think of “now” as being eternity; after all, “now” has a permanent existence even though it refers to different points of time, as time flows by. But it is this changing reference that “now” always has that disqualifies it from being eternity.
A5: If time is derived from changeable material creatures and eternity from the immutability of God, aeviternity is derived from the change that immaterial creatures may undergo; a kind of half-way-house between time and eternity. In this article Aquinas asks whether aeviternity differs from time. This is non-trivial since there appears to be a dichotomy: before and after exist (time); or they do not (eternity). Where does aeviternity fit?
Aquinas spends much of the reply demolishing competing ideas of aeviternity before turning to his own. His opinion is that aeviternity is associated with immaterial creatures that undergo no substantial change but which are accompanied in some sense with some accidental changes; “the further a thing falls short of abiding existence, the further it falls short of eternity”. One of the examples that Aquinas gives is the angels; he will show later on in the summa that they combine an unchangeable substance with changeable thoughts, affections and places (in a sense). So, for Aquinas, aeviternity is neither time nor eternity but somewhere in-between. Aeviternity should be thought of as being instantaneously whole, but able to co-exist with before and after.
A6: Since both time and eternity are unique, Aquinas asks whether the same is true of aeviternity. The objections suggest that the different types of things measured by aeviternity are so different they must have their own aeviternities.
Aquinas approaches the question by considering how we arrive at the conclusion that there is only one time, then extending the argument by analogy to aeviternity. Borrowing an argument from Aristotle, Aquinas claims that the motions in the world form a hierarchy. Motions lower down the hierarchy are measured in terms of motions of things higher up the hierarchy. Time measures “the most fundamental motion” at the top of the hierarchy and therefore time is a unity because all other motions are measured in terms of it.
Turning to aeviternity, Aquinas recognizes two opinions concerning immaterial things. The first opinion, which derives from Origen, suggests that all immaterial things were created equal. Aquinas argues that if that is the case, then this implies that each immaterial thing has its own aeviternity. Pseudo-Dionysius, on the other hand, claimed a hierarchy in immaterial things and that therefore lower members of the hierarchy are measured by the measure of the primary immaterial thing at the top of the hierarchy. Thus, making the analogy to time, there is only one aeviternity. Aquinas says that he will show that Pseudo-Dionysius’ position is the more likely (in Iaq.47.a2 & Ia.q50.a4); therefore Aquinas claims that it is more likely that there is only one aeviternity.
Summary & Handy Concepts
- Time is defined in relation to the succession of events in things that change.
- Eternity is defined in relation to things that do not change.
- God, since He is completely immutable, is eternal. In fact God is eternity.
- Eternity belongs properly only to God. However some things other than God can participate or share in God’s eternity in various ways. For example, necessary truths are eternal, existing in God’s mind.
- Time and eternity are really distinct as they are measures of different types of thing. Although we speak informally of unbounded lengths of time as being eternal, a more formal use rejects the idea of embedding time within eternity.
- Aeviternity is defined in terms of the changes that immaterial creatures can undergo. There is no before and after in aeviternity; it is instantaneous in a way similar to eternity. However the notions of before and after can coexist with it.
- The aeviternity of a being can be thought of as a participation in the eternity of God; the participation being stronger the closer the being is to God.
- Following Pseudo-Dionysius’s teaching on the hierarchy of immaterial creatures, we can infer that there is only one aeviternity as opposed to an aeviternity corresponding to each type of immaterial creature.
- Aquinas doesn’t say much at this stage about how time and eternity are related, other than to say that they are different. In the same way that it is very easy to misunderstand how God is present spatially, it is easy to be mistaken about how God affects created things in time.
- Though aeviternity is instantaneously whole, it differs from eternity in being able to co-exist with before and after. (Ia.q10.a5.ad 3). It is unclear how this works or how we might picture what this means. As with the relationship between time and eternity, Aquinas leaves many questions about the relationship between time and aeviternity unanswered.
- If we are to consider eternity as existing as an instantaneous whole, how are we to understand instantaneous? The very notion of the instantaneous derives from our perception and understanding of time.
- Although aeviternity is defined in terms of immaterial creatures and therefore applies to the souls of the blessed in heaven before the general resurrection, one might argue that it also applies after the general resurrection as well and therefore to some material creatures. The notion of the glorified body may be identified with a radical enhancement of the spirituality of the body, but it still remains material in some way.