In the following parts of the series, I will present and assess the merits of a number of objections to Aquinas’ argument. It is important to understand the background of the argument before undertaking an analysis of objections, so if you have not checked them out, I would suggest reading Part 1 and Part 2. For each objection, I shall explicate the reasoning behind the objection, followed by an “assessment” section which evaluates the efficacy of the objection in question. Without further ado, let’s examine the first criticism leveled against Aquinas.
The argument from change presupposes the falsity of eternalism and the truth of an A-theory of time. For consider that, under eternalism, all times are equally actual. Eternalism, in other words, entails the falsity of temporal becoming. It thereby denies the conjunction of the following theses: (a) one temporal state of reality is actual, (b) a future temporal state of reality is not actual (i.e. merely potential), and (c) there is a successive transition from actual temporal states of reality to future temporal states of reality, such that (i) the future states were merely potential, and (ii) the future states become actual. Without the conjunction of these three theses, though, the argument fails. For if (b) is false, then it is false that future temporal states are not actual (i.e. merely potential). But that means that future temporal states are already actual, in which case any change from a present state to a future state does not consist in the actualization of a potential state. P2, then, would be false. But if (c) is false, then there is no transition from actual states to potential states after all, even supposing (for the sake of argument) that there are merely potential states to begin with. But without there being any transition from actual to potential, then either P2’s analysis of change is false, or if P2 is true, then change itself does not exist (and P1 is false). Either way, the argument is unsound. Finally, the argument requires (a) since if no temporal state of reality is actual, then all temporal states of reality are either merely potential or (if they’re not even merely potentially existent) impossible (since something can only be possible if it has the potential to exist). But if all temporal states of reality are either merely potential or impossible, then since change requires a changer which is itself in a state of actuality (per P4), it follows that no temporal change exists after all. In that case, though, the justification for premise one is undercut, since the world of our experience consists of temporal things, and Aquinas explicitly adduces the evidence of our experience as demonstration of premise one.
From the preceding analysis, therefore, the argument’s success requires the conjunction of (a), (b), and (c), since the falsity of any one of them casts doubt on the argument’s cogency. But if eternalism is true, then arguably both (b) and (c) are false. This is because eternalism entails that the future is not merely potential but as equally actual as the present (and hence entails the falsity of (b)). Eternalism also entails that objective, successive, temporal becoming or transitioning is not a real feature of reality, in which case (c) is false as well
The fact that the argument from change presupposes the truth of an A-theory of time and the falsity of B-theories of time is (one may argue) by itself enough to make the argument unconvincing. If an argument A presupposes proposition P, but P is wholly unjustified (at least in the dialectical context at hand), then it seems A (or at least the conclusion of A) is itself unjustified (i.e. not sufficiently warranted by reasoning). For instance, if I argue that fine-tuning evidence shows a designer of the universe exists, but my argument merely presupposes that there is any fine-tuning evidence in the first place without justifying this presupposition, then my argument itself is unjustified (or, again, at least the conclusion of my argument). Hence, without justifying the falsity of eternalism, it seems Aquinas’ argument is not sufficiently warranted.
If, however, eternalism is in fact true, then the argument from change is not only unwarranted, but unsound. And, one may argue, there are good reasons for thinking eternalism is true. For suppose eternalism is false. Then, all times are not equally actual, i.e. some times are merely potentially existent. But for all times t, there are t-indexed truths (i.e. truths making essential reference to time t). This follows from the law of non-contradiction (LNC): for any proposition P, P is either true or its negation is true. Since for all times t, there is a t-indexed proposition to the effect that “at t, x exists”, and since per the LNC this proposition is either true or its negation is true, and since a negation of a t-indexed proposition is itself t-indexed, it follows that for all times t, there are t-indexed truths. But truths require actually existent facts or states of affairs that serve as truthmakers. That is, there must actually be something in virtue of which a given true proposition is true; the truth must correspond to something in actual reality. But if, for all times t, there are t-indexed truths, and if truths require actually existent facts or states of affairs that serve as truthmakers, then for all times t, there are actually existent temporal facts or states of affairs at t. In other words, for all times t, there are actual temporal things at t. But that entails that there are no merely potential temporal states, since if there were a merely potential temporal state, then there would be at least one t such that there is no actual temporal fact or state of affairs at t (thereby contradicting what we previously derived). Therefore, there are no merely temporal states. All temporal states are, therefore, equally actual. But that is just to say that eternalism is true. Hence, eternalism is true. In that case, though, the argument from change is unsound. Therefore, the argument from change is unsound.
Importantly, this objection from eternalism assumes that the only changes that exist are changes that are temporally extended processes. The objection, in other words, argues that because the existence of temporally extended changes (understood as actualizations of future potentials) entail that future times are not as equally actual as present times, and because eternalism entails that this is false, there cannot be temporally extended changes understood in act/potency terms. Crucially, though, Aquinas’ argument does not require the existence of temporally extended processes of change. All it requires is the mere existence of change and an analysis of change as the actualization of a potential. But this does not require future potentials being actualized. Arguably, there are purely present, instantaneous actualizations of potentials that do not require any future temporal states of reality to be merely potentially existent. Consider the example of a flower pot being sustained in mid-air right here, right now. Or consider two books, each leaning up against the other at the present moment. Or even consider a foot impressing upon the sand at a single moment. In each of these cases, we have some cause impinging upon its effect at a single instant. No durational, extended process is required in order for these cases to count as causation and (since causation is a kind of change) change. In each of these cases, there is a concurrent cause which is sustaining or actualizing a given state at a single instant, in which case there are actualizations of potentials (and hence “change” in a concurrent, instantaneous sense) that neither require nor entail extended processes through time wherein future states are merely potential. The actualizers in such cases are not temporally prior to the potentials that they actualize. Instead, they are in some sense causally or ontologically prior to the potentials. From this, we can see that the argument is, after all, compatible with eternalism, since the actualization of potential is not necessarily a temporally extended, linear process.
Moreover, this sort of ontological or causal priority is precisely the sense in which Aquinas seeks to motivate his argument. For consider his example of a chain of changes: “…subsequent movers move only inasmuch as they are put in motion by the first mover; as the staff moves only because it is put in motion by the hand.”8 By means of this example, Aquinas is emphasizing that the chains of changes with which he is concerned are ones in which less fundamental members of the chain move only insofar as they are moved by more fundamental members. That is to say, their motion or change is derivative from the changing activity of other members. This is seen most forcefully in the case of the staff moved by the hand. Importantly, the staff has no power on its own to move in this specific regard. Any change or motion it makes in this regard, therefore, must be derived wholly from without. Does it derive its motion in such a case from the hand? Well, the hand itself is being moved, at this instant, by certain neuromuscular firing patterns. The hand, by itself, is utterly powerless to move the staff unless it derives this power from a more fundamental member. But are the neuromuscular firing patterns the most fundamental member in this chain? It seems not, since these are only moving the hand insofar as their biochemical components are arranged, ordered, and changing in the precise manner in which they are, which in turn derive their changing power from (i.e. are actualized by) the more fundamental molecular changers, which in turn derive their changing power from atomic changers, which in turn derive their changing power from changers at the subatomic level. In each layer of this causal chain, we have a more fundamental member (changer) actualizing the state of the less fundamental layers. Importantly, this is not a series ordered throughout time, but is rather occurring at a single moment in time. Even at a single moment, the stick’s potential is being actualized right now by the hand, which in turn is being reduced from potency to act by neuromuscular activity, which in turn only actualizes the hand insofar as it is being actualized by biochemical and molecular activity, and so on.
This, in turn, illustrates the distinction between per se and per accidens chains. Per accidens chains are ones in which each member has causal power on its own and can exercise such causal power apart from all other members in the series. In other words, the causal power of one member does not wholly derive from all previous members in the series. A female boa can on rare occasions reproduce asexually. Suppose we have a chain of female boas reproducing asexually that extends backwards into an infinite past. Importantly, though, each female boa in the chain can causally bring about the succeeding boa without the continual operation of all past members. Each female boa, in other words, has underived causal power in this respect. Indeed, perhaps all the past members of this chain have died. Nevertheless, despite the previous members’ non-existence, a present member of the chain can still beget a further member. This series is a per accidens chain.
A per se chain, on the other hand, is one in which each member has no such independent, underived causal power. Take a series of power strips. Power strips, on their own, have no causal power to generate electricity. They only derive it from previous members of a chain. If one power strip conducts electricity, then it derives such electricity from without. Supposing it derives electricity from a yet further power strip, we are still left puzzled as to why there is any electricity being conducted, since this further power strip also has no power of its own to generate electricity and must itself derive electricity from without. In a chain of power strips, then, we can see that each member’s electricity is essentially dependent on previous members’ electricity, such that each one has electricity in a purely derivative manner. With the power strips, there is no independent causal power that can be exercised irrespective of previous members of the chain (as was the case in the series of female boas). This essentially dependent and derivative nature is the core feature of per se chains.
But because per se chains are not linearly extended throughout time, and because Aquinas’ argument concerns per se chains of change, it follows that his argument succeeds or fails irrespective of theories of time. Hence, eternalism does not pose a challenge to Aquinas’ argument.
Even if the foregoing analysis is mistaken, though, Aquinas’ argument can still be defended. For the argument offered in favor of eternalism founders on a misapplication of the truthmaker principle. The truthmaker for statement S is just the fact that S. As philosopher Edward Feser puts it, “The truthmaker for the statement that Julius Caesar was assassinated on the Ides of March is simply the fact that Julius Caesar actually was assassinated on the Ides of March, and nothing more need be said. In particular, we needn’t cash out claims about what was the case in terms of some claim about what presently is the case, or in terms of something that exists now. Facts about what was are as primitive as facts about what is, and irreducible to the latter.”9 Indeed, the entire core of A-theory is that not all times have the same kind of reality, and so it is wholly unsurprising that the truthmakers for propositions about, say, the future are unlike the truthmakers for propositions about, say, the present. The B-theorist will of course disagree, but the point is that to merely insist that all truthmakers must be of the same kind is flatly question-begging against the presentist.10
Finally, there are a number of motivations in favor of A-theory, from the ineliminability of tensed language, to our phenomenological experience of temporal becoming, to (arguably) the inadequacy of B-theoretic accounts of change. Exploring these in depth, however, would take us too far afield given present purposes. Suffice it to note that the objection from eternalism fails because (a) even under eternalism, there are still actualizations of potential (since Aquinas’ argument concerns per se series), and (b) the argument proffered in favor of eternalism founders on a question-begging application of a form of the truthmaker principle.
Stay tuned for the next post in series that will explicate another objection to Aquinas’ argument.
8. Aquinas, “Summa Theologiae,” ST I q2,a3.
9. Feser, “Aristotle’s Revenge,” 301.