On Time Travel

Deterministic fatalism is the view that all events are determined or predetermined by prior events, usually with the result that free will is an illusion. Anything that happens would always have happened that way, and no (material) events can occur that were not already determined after the state of the world has some sense of established cause and effect in order.

Whatever will be, will be.

I will argue here that deterministic fatalism has more than a single variety. Most humans do not live or act as if they believe that their present actions or decisions are necessary results of a long line of necessary cause-effect chains of actions and events. It seems to be, instead, that most believe that their actions and decisions make a difference. However much this may seem to be necessary (that we have at least limited free actions as agents in the universe), it seems that many people yet subscribe to a limited form of deterministic fatalism—namely, with regard to past events. While we may allow for options in the present and/or future, the past is thought to be “set in stone,” fatalistically determined even.

Whatever was, was.

Let us assume a fictional state of affairs to get at the heart of this argument (and have some fun while we’re at it). We have somehow invented a time machine and travel to the future. No really, this happened, and it was great. We meddled with events in the future and came back to our own original time. Is anything different? If you are not an absolute deterministic fatalist, then you might answer “No, nothing has changed.” Being in the future was not much different than affecting things in the present. It is present and past events that help to determine the future state of events—the future does not determine the past or present.

However, let’s say that we travel to the past, and influence some past event by our presence there. Now we travel back to our original time. What affect will our actions have on our original present state of affairs? You might say some kind of “butterfly effect”, tiny ripples in the past (like a butterfly being crushed) might lead to large consequences in the present and future (like a different Prime Minister in power). Or you might think a paradox might occur, such as killing one’s earlier self, a grandparent, or accidentally causing the time machine itself to have never been created. You might also respond that an alternate history would be created from this, separate from the original “time stream”, in which a different set of affairs were transpiring at the present due to a change in the past (through alternate universes, multiverses, or alternate causal time streams).

As a Christian, you might think, instead, that changes cannot occur in the past for the time traveler because of 1- God’s providence, 2- the immutability (unchangeable character) of the past, or because 3- direct access to the past is not possible (for theological, historical, or physical reasons).

But if we are free to make choices today (and tomorrow) that affect the future, even given providence, then why not in the past?

And is the past fundamentally immutable (unchangeable)? What makes it so, and must it be that way? Further, how do we know that the past cannot be changed? After all, all of our data up to now seems to suggest that the past has been changed over and over again—in the past. And if our argument is that the future cannot change the past, that argument is actually outside the purview of our case of a time traveler to the past, since the time traveler makes changes in the past from the past (i.e. her future actions do not affect the past, rather, her actions in the past affect later events).

If we argue that direct access to the past is not possible (on any grounds), then we disallow for the time traveler out of necessity. It is not truly time travel pure and simple (it seems to me) if our time traveler is not allowed access to change or interact with anything in the past. I think the real basis of this thought (of no direct access) is a belief in deterministic fatalism in the past. I think this is a variety of absolute deterministic fatalism, and it may be that belief in one may require belief in the other if it is to be coherent.

For instance, may not each argument made on behalf of deterministic fatalism of the past variety also be used on behalf of absolute deterministic fatalism (God’s providence, the present is immutable, direct access to the present is not possible, etc.)? Would this not force (if a person were believing rationally and coherently) acceptance of the absolute variety if the arguments of the past variety were acceptable? (Accept one and you accept both?)

At least this seems to me to be the case if a time traveler goes to the past. If it is the case that time travel is not possible (and not merely improbable), then deterministic fatalism of the past variety need not even come up. Of course, since the problem has arisen (if only in our argument here), even without the possibility of time travel, we may as well discuss it.

Do you believe the past is unchangeable? Is it fully determined and uneditable? What if it were not? What would that mean? How might the world be if we could edit the past? (Not merely edit the history books, but history itself?) Maybe we can! We edit the past in many moments throughout every day. Our actions are decided in the present, but their causal connection is in the future when we make these decisions, the actions cause effects that move to our past, and we then continue to act based on our edits of the past.

Take a cup of hot coffee for example. I make a decision to drink it right now, knowing full well that the decision is an event in the present that actually has an outcome in the near future, which will be past by the time I perceive that I have taken a drink, and I will continue to drink based on feedback about how good the coffee tastes in the past. I edited the past by taking a sip of the strong java (the past event of tasting the coffee was the result of an edit I made in the past). While I was deciding it, I was in the present deciding a future event, and when I was contemplating drinking more, I did so based in part on my past decision that affected my past (I already drank some after all). I edited the past by deciding on the future in the present.

And as a time traveler I would be in the present “in the past” (for instance, if I went back to my own birth). For me, at that time, it would be my present. For instance, I could hold my own infant hand as a present event. I would decide to do an action in the future (hold my baby hand) in the present, and this would edit the past, perhaps in just the same way as I edit my own past when drinking coffee.

You might ask “What if you accidentally slipped and landed on your baby self, and you killed your baby self in the past?” Paradox! (And a very bad day.)

Poof! I cease to exist, but then again I never was able to have killed my younger self if I died before I was able to go back in time, so I never died, but then I went back in time and killed my younger self, and on and on. Maybe this describes a time-loop? But what if deterministic fatalism of the past variety is not the case in our world? If changes can be made in the past (it is not wholly determined), then we can make changes in the present that do not irrevocably alter the future (or past or present). So a time traveler might accidentally kill their younger self, yet might not cease to exist in the present (and future) as an adult. They would just be dead as a baby. This might not cause a time paradox, even if they never grew to be an adult to be able to come back and accidentally kill themselves.

Here is the line of reasoning:

  1. Adult time traveler goes back in time
  2. Traveler kills younger self
  3. Younger self never grows up to be time traveler

From the point of view of the time traveler, however, here might be what happened:

  1. Time traveler is born
  2. Traveler grows up to invent machine to travel to the past
  3. Adult traveler goes back in time
  4. Traveler accidentally kills younger self
  5. Traveler continues to live their life in the past as an adult (or maybe they go back to their original time)

Maybe there is no time traveler’s young life in between their death as a baby and their future adult life. Maybe the past can be changed for the traveler so that their intermediate state was no more. But then who invented the time machine? Well, the time traveler seems to have invented it. How? He did in the past, the past that was edited. Now that he is back to the present, perhaps he did not exist at the time of the invention (after all, he died years earlier), but perhaps his non-existent self (or non-self) invented it. Or maybe he didn’t. Even given no inventor, and no time machine invented (in the future), still the time traveler might come to the original time in his non-invented time machine. We could posit a miracle if we wanted to, or we might argue that causality is still satisfied through earlier unedited history. Every causal link might still exist (in the edited past).

Again, if we have the choice to edit the future in the present, why not the past (by going back and editing the future from there)?

A further thought experiment: what if the time traveler went to the past and kidnapped his younger self, brought his younger self to his original time and dropped him off, then went back to the past and lived there as an older self (his younger self being stuck in his older self’s future). What happens if his past self uses the time machine after a while and travels again to the past in it? He can live his life over again (and edit it differently each time), sending his younger self to the future each time. What happens to his original younger selves in the future? Apparently each of them lives a life as normal (except they are at later points in time than they should be) and each grows old (older than their kidnapping self who is now in their past). Multiply-instanced selves? That’s what we had when we travelled back in time to visit our baby selves in the past anyway, isn’t it?

Granted, this is confusing and ridiculous. But remember that even though this is a ridiculous mess of a problem, the question is not “Should we travel into the past?” but “Can we travel into the past?” If we can in any meaningful way, deterministic fatalism of the past variety must not be an option. We must be able to make decisions in the past that edit the past in some meaningful way, and I have outlined here a bit of what this might look like (if it were possible).

To the point: don’t invent a time machine (I’m talking to you, future self). You don’t want to have to live with those kinds of decisions as a future past self.

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One thought on “On Time Travel

  1. As a determinist, I find most discussion about determinism to be irrelevant to my life. Determinism is not a belief, it is an understanding. Determinism teaches compassion. It can be something quite beautiful. The book “Aren’t We The Lucky Ones” by Secretary Michael tells the story of a group of determinists who form a community and live together in relative happiness. This is the kind of determinism that nourishes me. I hope I can find others who feel likewise.

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