Against ‘time-travel’

This is really just an announcement, of a new piece of mine that is coming out that I think many readers of this site may find of interest:
This my piece against-time-travel has been pre-published online in one of my favourite journals… 🙂
Comments welcome. (The full-length version will be forthcoming in my next book, and will contain more explicit stuff in it about Dr. Who…)

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  1. “When people assume that they have some concept with which they can state intelligible beliefs, these people may be mistaken. One example are certain beliefs about time travel. Suppose I claim that it might have been true that I had caused myself to exist, because I had traveled back in time and had earlier brought it about that my parents met. married, and had me as their first child. If you replied that my claim was not fully intelligible, you would be right. Other examples are some beliefs about time’s passage. lt can seem meaningful to say that we are moving through time into the future. or that nowness, or the quality of being present, is moving down the series of events from earlier to later, or that every day our death is getting closer. But such remarks, though they can seem deeply true, make no sense. There is nothing that could be intelligibly claimed to be what is moving through time. Nor could we explain what it would be for anything to move, not through space during some period of time, but just through time. Though our death is closer now than it was twenty years ago. that is merely like the fact that New York is closer to Washington than Boston is. This comparison may help us to sec the stillness of time.”

    Derek Parfit, ‘On What Matters’ – a book that’d be worth your while to read Rupert, if you find the time.

  2. My major complaint against your line of argument in the first part is that it would turn this excellent episode of Futurama into nonsense. Surely not, sir!

  3. Thanks both!

    Derek P. was a teacher of mine way back in Oxford, but I haven’t read his stuff for years (although, coincidentally, I am at present penning a movies-based objection to his central ideas about personal identity famously derived from the teletransporter cases). I will read On What Matters.

  4. Rupert,

    I forwarded your paper to the folks at CERN and they are most relieved. 🙂

    Objection to Parfit on PI and being beamed up and down? … are you going to argue that you don’t survive transporting down to the dangerous alien planet and back even if you don’t wear a red shirt?

  5. An excellent paper. All points made abundantly clear. An example of good philosophical writing. I accordingly look forward to reading more of Rupert’s published work, in due course.
    Any ideas how that neutrino apparently exceeded the velocity of light?
    “There was a young girl named Miss Bright
    Who could travel much faster than light
    She departed one day
    The Einsteinian way
    And came back the previous night”

  6. Thanks Don, Jim.
    On the CERN ‘result’: It may well turn out to be wrong. If it is right, it may well presage a scientific revolution in progress. But I don’t think it causes problems for me, even in that case. To see why, consider:
    (1) The points I make in this piece and in my earlier publications on time (see my APPLYING WITTGENSTEIN) about how relativity theory doesn’t create an _issue_ for my thinking, of any kind.
    (2) That my argument in any case is that, without travel ‘backward’ in time, there isn’t really any time-travel to speak of. If the CERN result is right, as I understand it, then it will not yield ‘backward’ time-travel. It will yield movement in the ‘space’ outside the light-cone. That isn’t the same as movement ‘backward’ in time. (And a good thing too: because (as I argued) there ain’t such a thing…) It would be very surprising; but not upsetting of my conceptual points.

  7. Good stuff. I was just thinking about this exact problem with the linguistics of time about an hour before I found this post. I like the way you put it.

    A couple notes on the less integral stuff:

    “She has to travel back into the past of all those people who do not travel back into their own pasts. If she is such a person, then she is not.”

    I’m guessing by “all” you mean “only”? And it might just be the way I read it but it sounds like you’re presupposing that nobody ever travels into the past. Maybe if you switch “do not” to “have not”?

    And on Lewis’ “The Paradoxes Of Time Travel” he doesn’t give a single reason because that’s like saying that everyone who failed a test got the exact same answers wrong. It could be any number of reasons. I’m not sure if it’s that paper or if it’s another one more concerned with counterfactuals but he does use counterfactual logic to explain that he’s not saying that you couldn’t do it, just that you won’t. We don’t know why you won’t, we only know that you didn’t, and in a bi-deterministic universe “won’t” and “didn’t” are essentially the same but “didn’t” and “couldn’t” are much different. I would agree that it’s flawed but I think it’s more a result of which worlds in this case he considers possible.

  8. Thanks Taylor. I think ‘All’ is better than ‘only’, but I don’t really mind.

    The thing is, Lewis just saying you won’t is, it seems to me, highly-unsatisfactory. WHY won’t you?
    I offer (the) reason.

  9. I agree it’s a cop out. But “it’s a cop out” isn’t itself the best argument either is all.

    And yeah, just wanted to clarify cus on a first read that paragraph sounded a bit like it could also have been trying to say that the travel itself is the contradiction as opposed to it creating a causal loop, but again, that was probably more the way I read it than the way it was written.

  10. Rupert,

    The CERN comments were flippant but not meant as dismissive.

    As was the case with my Star Trek reference to your intriguing sounding movie objections to beaming folk up and down and Parfit’s central ideas on personal identity. (I’m looking forward to finding out if the central ideas you object to are that questions on PI are empty, and that PI simply doesn’t matter for survival).

    Whatever the science ends up showing about neutrinos and backwards causation, I don’t think it will any have bearing on the validity of your argument.

  11. I do not think the early conclusion, “we are only prepared to call going to the future “travelling through time” if we can potentially return from the trip”, is sufficiently implied by the argument, nor that it is satisfactory in itself. I’ll focus on the latter objection.

    At a few points in the Back to the Future trilogy (which I unapologetically cite as the paradigmatic time-travelling tale) the protagonist Marty McFly, and in the second and third instalments also his friend Doc Brown, appear to be unable to return to their own times. First it seems that having landed in 1955 there is no way of producing enough electrical energy to power the machine’s “flux capacitor” component for the return journey, “back to the future” of 1985. In the second instalment a return from the future of 2015 to the ‘present’ 1985 (at least, to the 1985 they recognise as their own) is rendered impossible because the antagonist, Biff, has changed history behind them, creating an “Alternate 1985”. In the final film, Marty and Doc appear to be stranded in 1885. This time it is not the electrical energy they require (the machine is now fitted with a fusion device from the future) but kinetic energy – the time machine needs to travel at 88 miles per hour relative to their local space in order to achieve time travel, but “there won’t be a gas station around until sometime next century”.

    Doc Brown’s time machine, a converted DeLorean car, does not speed up or reverse the flow of time, like sleep, or like an HG Wells-style time machine. The DeLorean enables instantaneous travel between any two times programmable into the time circuits. Time travel has occurred at the same moment the traveller arrives, seemingly uncaused, by instantaneous “temporal displacement” at a new point in time. (The traveller’s position relative to the Earth is preserved in the journey. This is an unexplained fortuity as you point out, but it is not lethal per se to the notion of instantaneous “temporal displacement”.)

    I can only state that for myself – and surely others? – I am indeed prepared to say that skipping forward (or backward) over the intervening years in the time machine, Marty and Doc have time travelled, that this term applies immediately on arrival in a new time, regardless of the subsequent dramas in which the return journey is put in doubt.

    Likewise, even on your example of ordinary travel, I can be said to have travelled to Peru even I lose my return plane ticket or fall ill or decide to stay; in other words regardless of any other eventuality that prevents me from returning, travel has already occurred.

    If my position holds, then your premise that backwards time travel is a necessary condition of any time travel does not hold (forwards time travel does not imply backward time travel) and then the subsequent conundrums caused by backwards time travel (valid as they may be) are insufficient in themselves to render instantaneous forward time travel conceptually impossible.

  12. I disagree, Bob. I think that ‘Back to the future’ provides an object lesson in the nonsensicality of time-travel narratives, as do other famous cases, such as ‘Day of the Daleks’, the ‘Terminator’ trilogy, etc. . When you press hard on them, they fall part. One obvious place to press on even the first Bttf film, never mind the multiplyingly-sillier sequels, is the mad Professor’s knowledge the whole time that he was going to be ‘assassinated’ when he was old.

  13. Hi Rupert
    I agree, but my point isn’t that this trilogy in any way demonstrates that time travel is feasible.
    I only used it to argue against the idea that the public conception of time travel into the future necessarily involves a return journey. To re-state it in your phrasing: “we *are* prepared to call going to the future “travelling through time” regardless of whether we can potentially return from the trip”.

  14. Bob; ah, I see.
    Still don’t think you are right: [Isn’t it kinda right there in the title, ‘BACK to the future’?]
    Anyway, the important point about ‘Back to the future’ is that IT IS A JOURNEY INTO THE PAST. Remember the structure of my article: my point is that ‘time-travel’ into the _future_ ALONE is not enough. The first film’s structure already allows this point.

  15. But surely a definition of time travel that excludes any notion of ‘travel’ that does not include a return to the point of origin results in ‘travel’ not existing.

    In a strictly Heraclitean sense, that is.

  16. Talking Philosophy | Read Parfit Wrong - pingback on October 8, 2011 at 3:15 pm
  17. Really good stuff. Would any of you be interested in commenting at my blog or writing a guest post?

  18. Thank you for sharing this helpful information you provide for your articles.

  19. A Wittgensteinian way with paradoxes | Talking Philosophy - pingback on November 12, 2012 at 9:47 am
  20. Firstly: time travel into the past is not logical because – imagine that in your body are atoms which were in body of someone else who lived before you. So if you visit the time when that person lived then the same atoms will be in that person and in you. It is like multiplication of the same matter. It does not make any sense.
    Secondly: time travel into the future is also illogical.
    Objects in the motion despite they speed and supposed fractional movement in time are not disappearing even if they consider to be in different time! They are still in the same reality.
    Thirdly: experiments with atomic clock travelled and comparison them to stationary atomic clocks are right and consistent with the Einstein theory. However, those events does not indicating that the time travel is possible. They apply to time measurement in specific conditions. Because such devices and they principle of working (they particles)undergo what Einstein has told while traveling with certain speed. But extrapolating this to e.g. physiological systems like human being or any mechanical devices that work on different principles or to any solid materials for instance and expecting miracles is a great misunderstanding. because time is a measure undergoing conditions in which it is taken or observed from a different point of view (according to relativity theory) and abstract measure of motion of one movement compared to the other, but not the real thing. What we experience is only lasting and any movement can be observed.
    And rate of that movement, well, can be described as time.

  21. Jozef–Two excellent points. #1–The problem applies to your own atoms as well: if you visit yourself in the past, that’s already two copies of yourself, and ad infinitum for all time instances in between.
    #2–My version of this is this: reality means that you are part of the Universe. Time dilation, etc., do not remove you from this Universe. Photons never age, yet they live for billions of years while traveling from the edge of the Universe to here and now. I think that your point (3) is thus very similar to point (2).

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