The dreaded causa sui

There is no case known (neither is it, indeed, possible) in which a thing is found to be the efficient cause of itself; for so it would be prior to itself, which is impossible.

Summa Theologiae I.2.3

If, then, something were its own cause of being, it would be understood to be before it had being – which is impossible…

Summa Contra Gentiles I.22.6

Was Aquinas mistaken? Could something be its own cause? Stephen Hawking and Leonard Mlodinow seem to think so. In their recent book The Grand Design, they tell us that “we create [the universe’s] history by our observation, rather than history creating us” and that since we are part of the universe, it follows that “the universe… create[d] itself from nothing.”

I examine their position (and the many things that are wrong with it) in my review of the book for National Review. What is of interest for present purposes is their suggestion that future events can bring about past ones. Could this be a way of making plausible “the dreaded causa sui” (as I seem to recall John Searle once referring to the idea in a lecture)? That is to say, might a thing A possibly cause itself as long as it does so indirectly, by causing some other thing B to exist or occur in the past which in turn causes A?

To be sure, Hawking and Mlodinow provide only the murkiest account of how their self-causation scenario is supposed to work, and do not even acknowledge, much less attempt to answer, the obvious objections one might raise against it. But one can imagine ways in which such a scenario might be developed. Suppose for the sake of argument that the doctrine of temporal parts is true. And suppose we consider various examples from science fiction of one temporal part or stage of an individual playing a role in bringing about earlier parts or stages of the same individual.

In his 1941 short story “By His Bootstraps,” Robert Heinlein presents a tightly worked out scenario in which his protagonist Bob Wilson is manipulated by time-traveling future versions of himself into carrying out actions that put him into a series of situations in which he has to manipulate his past self in just the way he remembers having been manipulated. That is to say, temporal stage Z of Wilson causes temporal stage A of Wilson to initiate a transition through various intermediate Wilson stages which eventually loop back around to Z. In the 1952 E.C. Comics story “Why Papa Left Home” (from Weird Science #11), a time-traveling scientist stranded several decades in the past settles down to marry (and later impregnate) a girl who reminds him of the single mother who raised him, only to discover, after his abrupt and unexpected return to the present and to his horror, that she actually was his mother and that he is his own father. Doubling down on this Oedipal theme in what is probably the mother of all time travel paradoxes, Heinlein’s ingenious 1959 short story “– All You Zombies – ” features a sex-changing time-traveler (“Jane”) who turns out to be his own father and his own mother. (Don’t ask, just read it.)

Now, if we think of each of these characters as a series of discrete temporal parts – again labeled A through Z for simplicity’s sake – then we might say that each part has a kind of independent existence. A, B, C, D, and on through Z are like the wires making up a cable, in which each wire can be individuated without reference to the others even though they also all make up the whole. The difference would be that while the wires are arranged spatially so as to make up the cable, the stages in question are arranged temporally so as to make up a person. And what we have in the science-fiction scenarios in question is just the unusual sort of case wherein some of the stages loop back on the others, just as some of the wires in a cable might loop back and be wound around the others.

Mind you, I do not in fact think any of this is right. I do not accept the doctrine of temporal parts, and I do not think that such time travel scenarios really are possible even in principle given a sound metaphysics. (I’ll have reason to address these issues in detail in forthcoming writing projects, so stay tuned.) But as I say, we’re just granting all this for the sake of argument. And if we do, it might seem that we are describing a kind of self-causation.

In fact we are not, at least not in the sense of “self-causation” that Aquinas is ruling out as impossible in principle. For notice that in order to make sense of the scenarios in question, we have had to treat each of the stages of the persons involved as distinct, independent existences. For instance, in “– All You Zombies –“ it is, strictly speaking, not that Jane causes herself/himself to exist so much as that the later stages of Jane cause earlier stages of Jane to exist. And since each stage is distinct from the others, we don’t really have a case of self-causation in the strict sense. For none of the stages causes itself – each is caused by other stages. The situation is analogous to the “self-motion” of animals, which Aristotle and Aquinas point out is not really inconsistent with their principle that whatever is moved is moved by another, since such “self-motion” really involves one part of an animal moving another part.

We might also compare these scenarios to the kinds of causal series ordered per accidens that Aquinas is happy to allow might in principle regress to infinity. The stock example is a father who begets a son who in turn begets another. Each has a causal power to beget further sons that is independent of the continued activity or inactivity of any previous begetter. Contrast a causal series ordered per se, the stock example of which is a hand moving a stone with a stick. Here the stick’s power to move the stone derives from the hand, and would disappear if the hand were to stop moving. In the strictest sense, it is not the stick which moves the stone, but the hand which moves it, by means of the stick. By contrast, if Al begets Bob and Bob begets Chuck, it is Bob who begets Chuck, and in no sense Al who does it. The reason the latter, per accidens sort of causal series might in principle regress to infinity, then, is that the activity of any member does not of necessity trace to the activity of an earlier member which uses it as an instrument. But things are different with a per se casual series, in which no member other than the first could operate at all were the first not working through it. (I had reason to say more about the difference between these sorts of causal series, and about what is meant by “first” in the expression “first cause,” in this recent post.)

Aquinas allows for the sake of argument that the universe might have had no beginning, given that the series of causes extending backward in time is ordered per accidens. When he argues for God as first cause of the world, then, he does not mean “first” in a temporal sense. His argument is rather that the universe could exist here and now, and at any particular moment, only if God is conserving it in existence, for anything less than that which is Pure Act or Being Itself could not in his view persist for an instant unless it were caused to do so by that which is Pure Act or Being Itself, to which it is related in a per se rather than per accidens way. In particular, anything which is in any way a compound of act and potency (as all compounds of form and matter are, and, more generally, as all compounds of existence and essence are) must be continually actualized by that which need not itself be actualized insofar as it is “already” Pure Actuality. (See Aquinas for the details.)

Now every temporal part of the characters in our hypothetical science-fiction examples is relevantly like the particular moments in the history of the universe. Even if the universe had no beginning but regressed back in time to infinity, it would still have to be sustained in being at any particular moment by God. It could not at any particular moment be causing itself. And even if the temporal parts of the characters in question looped around back on themselves, they would still at any particular moment have to be sustained in being by God. They too could not at any particular moment be causing themselves. In short, the theoretical possibility of a circular temporal series would be as irrelevant to Aquinas’s point as the theoretical possibility of an infinite temporal series is. When Aquinas denies that anything can cause itself given the absurdity of a cause preceding itself, what he is most concerned to deny is, not that a cause can be prior to itself temporally (though he would deny that too), but that it can be prior to itself ontologically, that it could be more fundamental than itself in the order of what exists at any given moment, as it would have to be if it were sustaining itself in being. (And again, in any event no cause strictly exists prior to itself even temporally in the scenarios we’ve been describing; for each temporal part of the characters in question is caused by a distinct temporal part, not by itself.)

Hence, even if the universe were (as it is not) as Robert Heinlein or Stephen Hawking describes it, it would require at any particular instant a cause distinct from it in order for it to exist at that instant. (The same would be true if we consider the universe as a single four-dimensional object. It would still be a composite of form and matter and essence and existence, and thus of act and potency, and could therefore not in principle exist were it not caused by that which is not composite in any of these ways but just is Pure Act and Being Itself.) When we carefully unpack what the scenarios would have to involve, we can see that they do not entail any sort of causa sui, nor anything that could in principle exist apart from a divine first cause.