#838 Leftow’s “Time-Traveling Trinity”

Dr. craig’s response

Oh, man, don’t get me started on this one, Nolan! I have an extensive discussion in my projected systematic philosophical theology of Brian Leftow’s doctrine of the Trinity appealing to the analogy of time travel. In my opinion, this is the zaniest model of the Trinity on offer today! I should hardly find it worth discussing, except for the fact that it provides the most plausible model for an anti-Social Trinitarian, one-self model of the Trinity. Let me try to summarize my thoughts succinctly.

The biblical data concerning the “I-Thou” relations in which the Trinitarian persons stand and their mutual personal interactions constitute a crushing objection to one-self theories of the Trinity in general. But Leftow would explain these data on the analogy of the way in which a time-traveler can, by following time-like loops into the past, encounter and interact with himself, even returning to the same point in time arbitrarily often, so that to all appearances multiple persons are then interacting, when, in fact, there is really only one person who is present multiple times over interacting with himself. Leftow proposes that God similarly lives His life in three discrete, infinite life-streams as Father, Son, and Holy Spirit that overlap and so permit personal interaction. So when we read in the Gospels that at the baptism of Jesus the Father says, “Thou art my beloved Son. With thee I am well-pleased” and the Holy Spirit descends upon Jesus, what we have is God’s speaking to and interacting with Himself three times over. Just as a time-traveler can interact with himself during periods of overlap, so God can interact with Himself in the ways described in the Gospels.

Now Leftow doesn’t think that God, like the time-traveler, literally pursues time-like loops in order to encounter Himself repeatedly. Nonetheless, the time travel analogy is crucial for the plausibility of Leftow’s one-self account. Absent the analogy afforded by travel along time-like loops, nothing remains to make Leftow’s account plausible. So Leftow admits that he must defend the metaphysical possibility of time travel.

But does he do so successfully? I don’t think so. In defense of the metaphysical possibility of time travel, Leftow responds briefly to two standard objections to time-travel. The first concerns the famous paradoxes of time travel. The most well-known of these paradoxes is the so-called grandfather paradox, according to which a time traveler journeys into the past prior to his birth and kills his grandfather, thereby preventing his own existence and thus his travelling into the past. Leftow would avoid the paradoxes by maintaining that it is metaphysically possible that the time traveler lacks libertarian freedom and so is not able to kill his grandfather.

Leftow’s response seems to me doubly defective. First, the denial of libertarian freedom is not sufficient to avoid the problem because the paradoxical scenarios need not involve libertarian agents at all, but, as John Earman has shown, can be generated by time-travelling machines. Perhaps Leftow would say that it is possible that God determines that such machines are never built as well as that personal agents never attempt to engage in self-defeating acts. But that leads to the next point.

Second, what Leftow envisions is surely metaphysically impossible. He’s asking us to suppose that God might create creatures which are to all appearances qualitatively similar to human persons but which are in fact puppets wholly determined by Him. That seems morally unconscionable and therefore incompatible with the moral character of God.

The second standard objection, even more powerful than the paradoxes, is that time travel can lead to situations involving vicious explanatory circularity. Consider a case in which the time traveler confronts his younger self in the past. Suppose further that the younger self receives from his older self the information on how to build a time machine and that this is his only source of this information. In such a case the younger self gets the information from the older self, and the older self gets it from the younger self. While there is no logical contradiction involved in such a state of affairs, surely this sort of circular causation is metaphysically impossible. Leftow’s response is simply to accept that such explanatorily circular situations can obtain unless some unacceptably strong Principle of Sufficient Reason is a necessary truth. Leftow seems mistaken in this assertion, however. One need not adopt overly strong versions of PSR to esteem plausibly that such viciously circular situations are metaphysically impossible.

It seems to me therefore that Leftow has failed to turn back the force of the standard objections to time travel scenarios. But this is, in fact, only part of the story, indeed, I should say, a minor part. There are significant, independent reasons not even considered by Leftow for rejecting time travel as metaphysically impossible.

First, time travel is precluded by the objectivity of tense and temporal becoming. Defenders of time travel are explicit in their espousal of spacetime realism or four-dimensionalism, which entails a tenseless theory of time. But time is plausibly tensed and temporal becoming is real, and therefore time travel from the future into the past is metaphysically impossible.

Second, Leftow’s time travel scenario is on a collision course with the principle of the Indiscernibility of Identicals, the principle that if X and Y are identical, then they share all the same properties. The conflict arises as a result of the so-called problem of temporary intrinsics. The problem of temporary intrinsics concerns the question how an identical object can exist at two different times with different properties. The tenseless time theorist has a ready solution: the time traveler is really a four-dimensional object, and two temporal parts of the time traveler appear simultaneously in public time, and in virtue of their discernibility (e.g., different memories) are non-identical. Thus, the Indiscernibility of Identicals is preserved.

Leftow himself denies, however, that the time traveler is a four-dimensional object composed of temporal parts. Like the tensed time theorist, Leftow holds that the whole of the time traveler appears at a time and not just a temporal part of him. On this account the identical person appears twice at the same time with discernible properties. This situation is ruled out by the Indiscernibility of Identicals. It is impossible for the same person to have different properties at the same time. It follows that time travel scenarios such as Leftow envisions are metaphysically impossible. Leftow realizes that he has a problem here and tries valiantly to extricate himself from it, but to my mind unsuccessfully.

All this has been said with respect to the metaphysical possibility of time travel to one’s past. But now it needs to be asked whether even granted his suppositions, Leftow’s model offers a plausible account of the biblical data concerning the relations of Father, Son, and Holy Spirit. I take Leftow’s model seriously because it offers the best chance of reconciling a one-self view of the Trinity with the biblical accounts. But though the best of a bad lot, Leftow’s theory does not do justice to the personal relations and personal interactions between the Father, Son, and Spirit. It is not credible that the person who dies on the cross is the same person that sent the Son into the world. William Hasker has rightly protested,

In the Gospels, we have the spectacle of God-as-Son praying to himself, namely to God-as-Father. Perhaps most poignant of all (and this should be no surprise) are the words of abandonment on the Cross: ‘My God, why have you forsaken me?’ On the view we are considering, this comes out as ‘Why have I-as-Father forsaken myself-as-Son?’ To some of us, this just doesn’t seem to be what the Gospels are saying (Metaphysics and the Tri-Personal God [Oxford University Press, 2013], p. 118).

Leftow replies that if one concedes the coherence of the time travel scenarios, one “will find nothing particularly outré in a story of one person at one point in his life begging the same person at another point.” Leave aside the moot point whether the time travel scenarios are coherent. We can, indeed, imagine one temporal part of a time traveler begging a later temporal part not to shoot him, for example; but I can only agree with Hasker that that does not seem to be what the Gospels are saying about the Father and the Son. Should we really understand these narratives as God’s talking to Himself? Tertullian’s satirical retort to the Modalist seems apropos: “If you want me to believe Him to be both the Father and the Son, show me some other passage where it is declared, ‘The Lord said unto Himself, I am my own Son, today I have begotten myself’.”

The Gospels to all appearances portray the Father, Son, and Holy Spirit in inter-personal relationships. There is no justification for denying appearances and importing into the narratives time travel analogs to the three persons. Indeed, so to do makes the Gospel narratives of the inter-relations of the Father, Son, and Holy Spirit a pretense and a deception unworthy of God.