Firstly, this is a thought experiment -- I am aware that time is a "one way street."

I think this question may be inappropriate for the forum, so I would greatly appreciate a referral to a more appropriate medium (and if you have the time, a serious answer before its closing).

My question is this:

Is it possible to correct a seeming causal paradox by simulating the "cause"?

For instance, say that I forget to turn in a write-up and travel "back in time" in order to turn it in on time. As far as I can tell, this would create a paradox -- if the paper were turned in "on time," it would be unnecessary for me "go back" and turn it in in the first place.

However, say that I complete the write-up, regardless of having already received a notice of its completion. Would this allow me to continually "go back" and turn it in?

I apologize, and I am certain that there are better examples that more appropriately depict this question. There is obviously something "not right" with my logic, but I am having trouble breaking it down. Would anyone be able to help?


  • I made an edit which you may roll back or continue editing. Welcome to this SE! Commented Nov 14, 2018 at 11:08

3 Answers 3


Casual paradoxes are an inherently flawed philosophical concept to begin with. If you go back in time, the most reasonable assumption is that everything that you experienced will continue to be true for you. While you may (in theory) alter the past from everyone else's perspective, that does not mean you can undo the things that motivated you to time travel.

Instead consider that in your own personal perspective, going back in time is just like going forward in time in an uninterrupted series of personal experiences. If this is the case, then causation is not violated.

Consider these three models of time-travel to choose from:

Scenario A - Your older self goes back and co-exists with your younger self. You make a new future for your past self. Because of this he never goes back in time and he experiences a different future than you would have, but his past is not your past; so, you still have the shameful past experience of missing your deadline, while he goes on in ignorance of a future that he will never need to experience.

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Scenario B - You become your younger self and re-live your past experiences with the option to make new choices. You fix the mistake yourself, then you go on with your new future, but you still have the shameful past experience of missing your deadline.

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Scenario C - You change the past and (then for no reason) your own past rubberbands to account for this. While this is a popular model for science fiction, it would mean that 100% of time travel would create paradoxes. The existence of these paradoxes is actually what rules this out as a realistic expectation of how time-travel would work if it were possible.

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In models A & B, what caused you to change the Universal timeline is still true in your Personal timeline. So to answer your question, you probably cannot really stimulate the cause or create an infinite time loop because time-travel would always cause a divergence no matter how hard you try to make it loop. The closest thing to a time Paradox you could have is if you were to follow the B-model of time travel and you continue to go back in time to correct an unfixable mistake or just because you want to experience eternal life, but eventually that person would give up or die in a freak accident; so, at most you could create a long-loop, like someone walking around in circles until they get tired and stop.

  • Would you have any references to people who take a similar view? This would give the reader a place to go for more information and strengthen your answer. Welcome to this SE! Commented Nov 15, 2018 at 21:06
  • Paraconsistent logic is basically the science of Paradoxes. en.wikipedia.org/wiki/Paraconsistent_logic While on the surface, it seems to support paradoxes, when you evaluate it, you realize that a "Paradox" is sometimes true and sometimes false, but not true and false in the same case. Casual paradoxes are both true and false in the same case so there they defy paraconsistent logic.
    – Nosajimiki
    Commented Nov 15, 2018 at 22:42
  • A second reason to disbelieve Scenario C is to reason that if time travel is in fact "travel", then the most analogous model we have of it is moving through physical space. Model C assumes that if you travel from New York to Denver, and then back, then you will have a car that is identical to what you left in, when in reality it will retain all of the "ware-and-tare" of its travels. If you traveled back in time without retaining the ware of your future, then you could not change the past... and you've literally done nothing.
    – Nosajimiki
    Commented Nov 15, 2018 at 22:42

Nice question! It does seem like a plausible mechanism that we could take the weak point in a paradox and fix it. Unfortunately, I don't think it will work. Instead, I think your plan still results in a paradox--- a paradox that is a little harder to see.

In your proposal, here's what happens:

You have a write-up to submit. You receive a notice that it has been completed. Then you do the work and complete the write-up, and go back in time to submit it.

Let's freeze time right when you receive the notice. Why did you receive a notice that the write-up was completed?

If your answer is "because I traveled back in time and submitted it", then that's false: you have not traveled back in time. That's something you're planning to do, but you don't know if the time-travel machine will malfunction, if your long-lost brother will come and steal the machine, if you will have a heart attack and never use the machine, etc. And this is the critical part: the universe doesn't know these things, either.

So the notice you receive is either a mistake (which doesn't fit your premise) or it is impossible: nothing has caused this notice.


I dont think it is a paradox in the way you are stating because there is no infinite loop. You wrote the paper regardless if it was turned in on time or not. So traveling back in time you simply turned it in on time and have no need to travel back in time after that.

The second part does not make any sense to me. What type of notice? And how is it possible you would receive it before completion of write-up? To be more clear, are you saying you wrote the write up after the due date? If this is the case then you have created an infinite loop of needing to travel back in time because nothing has changed in the past because you will not write the write-up until you are late in turning it in.

There may be some paradox to the example other than an infinite loop in time travel, but from what I understand about paradoxes, to me the “time travel” part is not necessarily illogical, just not yet possible. (I have no opinion here)

  • The paradox isn't the infinite loop, but the contradiction between "I was late" and "I wasn't late". Commented Nov 14, 2018 at 20:57
  • At the top you say time is a “one way street”, but in this thought experiment it is a two way street, right? Time travel.
    – Robus
    Commented Nov 14, 2018 at 22:34

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