Creationism and time travel

Philip Henry Gosse famously (or infamously, depending on your viewpoint) distinguished between prochronic time and diachronic time. Gosse viewed nature as cyclical. Therefore, the only way to start the natural process was to kickstart the process by instantiating the cycle (or set of cycles) at some point during the cycle. So that generated a distinction between the ideal age of a natural object by divine fiat from and its real age.

The theory is unsusceptible to direct scientific attack, for the beauty of the theory is that it saves appearances. It’s a global theory that’s empirically equivalent to the competition. Consistent with whatever scientific evidence you throw at it.

You might try to attack in on those very grounds: claim it’s pseudoscience precisely because the theory is immune to scientific falsification. However, given the indeterminate status of theoretical entities, the problem of verisimilitude, and the underdetermination of theory by data, theories are resistant to straightforward falsification.

Because that line of attack is abortive, the objection shifts from scientific objections to ethical objections. God would be deceptive if he created a situation in which there was a discrepancy between ideal time and real time. In assessing that objection, it’s interesting to compare Gosse’s philosophy of time with the philosophy of time travel.

David Lewis was a distinguished philosopher who defended the coherence of time travel. He did so by distinguishing between external time and personal time. Among other things, he said:

Time travel, I maintain, is possible. The paradoxes of time travel are oddities, not impossibilities.

What is time travel? Inevitably, it involves a discrepancy between time and time. Any traveler departs and then arrives at his destination; the time elapsed from departure to arrival (positive, or perhaps zero) is the duration of the journey. But if he is a time traveler, the separation in time between departure and arrival does not equal the duration of his journey. He departs; he travels for an hour, let us say; then he arrives. The time he reaches is not the time one hour after his departure. It is later, if he has traveled toward the future; earlier, if he has traveled toward the past. If he has traveled far toward the past, it is earlier even than his departure. How can it be that the same two events, his departure and his arrival, are separated by two unequal amounts of time?

Instead I reply by distinguishing time itself, external time as I shall also call it, from the personal time of a particular time traveler: roughly, that which is measured by his wristwatch. His journey takes an hour of his personal time, let us say; his wristwatch reads an hour later at arrival than at departure. But the arrival is more than an hour after the departure in external time, if he travels toward the future; or the arrival is before the departure in external time (or less than an hour after), if he travels toward the past.

We can say without contradiction, as the time traveler prepares to set out, “Soon he will be in the past.” We mean that a stage of him is slightly later in his personal time, but much earlier in external time, than the stage of him that is present as we say the sentence.

In the same way, an event in a time traveler’s life may have more than one location in his personal time. If he doubles back toward the past, but not too far, he may be able to talk to himself. The conversation involves two of his stages, separated in his personal time but simultaneous in external time. The location of the conversation in personal time should be the location of the stage involved in it. But there are two such stages; to share the locations of both, the conversation must be assigned two different locations in personal time.

A time traveler who talks to himself, on the telephone perhaps, looks for all the world like two different people talking to each other. It isn’t quite right to say that the whole of him is in two places at once, since neither of the two stages involved in the conversation is the whole of him, or even the whole of the part of him that is located at the (external) time of the conversation. What’s true is that he, unlike the rest of us, has two different complete stages located at the same time at different places.

I answer that what unites the stages (or segments) of time traveler is the same sort of mental, or mostly mental, continuity and connectedness that unites anyone else. The only difference is that whereas a common person is connected and continuous with respect to external time, the time traveler is connected and continuous only with respect to his own personal time.

It remains true at all the personal times of Tim’s life, even after the killing, that Grandfather lives in one branch and dies in the other.

"The paradoxes of time travel." American Philosophical Quarterly 13 (1976).

Notice that he deploys his distinction between external time and personal time to finesse how a time-traveler who encounters his younger self is still one person rather than two–appearances notwithstanding.

Now one can debate the philosophical merits of his analysis. However, would it be reasonable to attack his explanation on ethical grounds? Is his distinction between external time and personal time deceptive?

We might still conclude that time travel is scientifically infeasible or subtly incoherent, but should we reject time travel because it requires us to distinguish between appearance and reality, one kind of time and another kind of time? If not, why is this model of time travel morally innocent, but Omphalism is morally culpable?