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, Part 2, Part 3, and Part 4. 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 third criticism leveled against Aquinas.
Suppose we have a process of change. We then have three things: the actualizer, the potential actualized, and the event of the actualizer actualizing the potential. Let C be the actualizer/changer (i.e. let C be the cause of the change). Let P be the potential that C makes actual (i.e let P be the effect of the change). Let E be the event of C’s making P actual. But suppose further that the causal principle (P4) is true, in which case anything that reduces from potency to act is actualized by something else already in act. Crucially, prior to C’s actualizing P, E was merely potential, since E is the event of C’s actualizing P. Once C actualizes P, then E is made actual. But that entails that E reduces from potency to act, in which case (per P4) it requires actualization by something else. But what caused or actualized E? P cannot actualize E because P’s very actual existence depends upon the obtaining of E! After all, if E did not obtain, then P would never have been made actual in the first place. P thus depends on E and cannot, therefore, actualize E. E cannot actualize E, since that would entail the absurdity of self-causation. Could C actualize E? It seems not. For consider that E is the link between C and any arbitrary potential effect P of C. If C actualizes E, then E is the effect, not the very link between C and any of C’s effects. But if neither E, C, nor P actualize E, then it seems E is a counterexample to P4, since it reduces from potency to act without anything else causing or actualizing it to do so. But suppose Aquinas could get around this and hold that C does, after all, actualize or cause E. An infinite regress, though, looms on the horizon. For now we have the event E1 of C’s making E actual. And this event transitions from potency to act and hence requires a cause. But if C is the cause of E1, then there is a yet further event, E2, of C’s actualizing E1, and a further event E3 of C’s actualizing E2, and so on ad infinitum.14 Thus, even if Aquinas could hold that C makes E actual, he does so at the cost of introducing an infinite series of actualizations of potentials, the very thing he denied in P12.
Aquinas therefore faces a dilemma. Either infinite series of changes are impossible, in which case Aquinas must deny premise four; or premise four is true, in which case Aquinas must deny premise 12. The conjunction of P4 and P12, then, cannot be true. But if that is the case, then Aquinas’ argument is unsound. Hence, Aquinas’ argument is unsound.
A number of philosophers have puzzled over metaphysical bootstrapping in relation to human free will, and solutions to those puzzles can be introduced on behalf of Aquinas in response to this objection. Many such solutions appeal in some form or another to a basic act in the sense of being a primitive and singular exercise of causal power which actualizes some things by means of causation and other things, like the event of its causing any effect at all, by means of logical entailment. To cash this out, Rasmussen writes (using e for effect and c for cause) that “as a result of this basic act, a couple things logically follow: (1) e is actual, and (2) c’s actualizing e is actual. These things that follow are not themselves actualized by any basic act of actualization. It is not as though c must actualize the state e is actual in order to actualize e. Rather, e is actual is ‘actualized’ in a derivative way… by a combination of c’s basic act of actualizing e together with logical entailment.”15 In conclusion, then, we avoid an infinite regress of changes, since C only directly actualizes P. The “actualization” of E is just the conjunction of C’s actualizing P in a basic manner plus logical entailment. We also preserve P4 since E is, after all, reduced from potency to act by something else in a state of actuality — namely, the actual laws of logic in conjunction with the actual existence and exercise of C’s causal power in actualizing P. P4 does not require that all actualizations of potentials be identical in kind (i.e. results of direct, basic acts of actualization). It only requires that something else in a state of actuality actualizes a given change. Overall, then, the bootstrapping objection is not successful.
In the next post, we will examine the nature of infinity and its relation to Aquinas’ argument.
14. Rasmussen, “How Reason Can Lead to God,” 49-50.
15. Rasmussen, “How Reason Can Lead to God,” 50.