The 1984 events in the original Terminator don't change the future - rather, the events are consistent with a single "version" of 2029, the 2029 seen in the film. This is evidenced by the fact that John Connor is Kyle Reese's son, and also reiterated by the photo of Sarah Connor taken at the end of the film.

However, the events in Terminator 2 did change the future. This is most directly indicated by the events and dialogue of Terminator 3, but even if we disregard Terminator 3, the destruction of Miles Dyson and his technology is certainly not consistent with the future that the T-800 and T-1000 are sent back from.

Thus, why was one set of events able to change the future, and the other set not able to?

  • 2
    Hmm, now that you say it, the two movies indeed seem to follow entirely different time travel concepts. While the first movie presents a completely unchangable time continuum adherent to the Novikov principle, the following movies indeed seem to allow the possibility of changing the future. I've never realized this discrepancy before, excellent question. I'd say Cameron (and any following writers) didn't really consider what a perfect and self-consistent time travel interpretation they had in the first movie and just scrapped it in the following movies for the sake of a more hopeful future.
    – Napoleon Wilson
    Dec 13 '14 at 2:47
  • I was wondering what the name of that physical principle was. It's pretty commonly used in time travel movies. Dec 13 '14 at 4:20
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    You mean that one? (As also prominently featured in another recent blockbuster.)
    – Napoleon Wilson
    Dec 13 '14 at 13:20
  • @NapoleonWilson yeah I was thinking of this and this Dec 13 '14 at 14:10
  • The events of Terminator I did change the future. The cpu and the arm were left behind which Cyberdyne used to build skynet.
    – Ben Plont
    Feb 12 '15 at 18:25


Terminator 1 appeared to follow the predestination ideology, where going back in time meant that John Connor and Kyle Reese fulfilled their roles, rather than changing anything.

Terminator 2 played much more with the idea of both fate and free will. By exercising free will, the future was changed. Of course it can be argued that intent is meaningless and that both films should have changed the future.

Yet, it's also quite logical that if you can go back in time to change things, you must sometimes (inadvertently) fulfil things as well.

On an out-of-universe final note - the Terminator time line is a bit screwy. Any basic googling will show that. You basically have to take it or leave it :)

Long Answer

I would argue that James Cameron simply considered the concept of time travel much more in the second film.

To quote from a Terminator predestination paradox wiki:

The predestination paradox was an integral part of the first movie in the Terminator franchise: The Terminator. There are two main examples where a future time traveler goes back in time and fulfills their role in history (rather than changing it):

  1. Kyle Reese fathering John
  2. The T-800 endoskeleton being left in the Cyberdyne factory.

The predestination paradox is heavily tied to the concept of fate. The photograph of Sarah Connor by the Mexican boy is an example of this: the photo that Kyle had in the future is exactly the same as the one taken of Sarah at the end of The Terminator. This heavily suggests that the events of The Terminator fulfilled the predestination paradox: The Terminator and Kyle Reese traveled back in time to fulfill their roles in history, not to change it.

Now, as many, many, many people have asked, how does this make any sense? Ultimately, the only reason John Connor is born is because he sends his father back in time to meet his mother, thus producing him - producing no end of apparent paradoxes. Quoting from the first article above:

Therefore, the only reason either John Connor or the machines exist is because the Terminator went back in time, and the only reason the Terminator went back in time is because the machines and John Connor exist. Get it?

Oh, and John Connor and our heroes spend the last act of the second movie trying to prevent said war, meaning John Connor is trying to prevent his own existence, by eliminating the reason for his dad to travel back in time to conceive him. And, if he does prevent his own existence, well, he certainly won't be around to prevent the war thus prevent his existence and...

Well, you get the idea.

Once we reach the second film though, suddenly this idea of predestination seems to change. Consider these quotes from the film:

Reese: Don't quit, Sarah. Our son needs you.
Sarah (struggling not to cry) I know, but I'm not as strong as I'm supposed to be. I can't do it. I'm screwing up the mission.
Reese: Remember the message... the future is not set. There is not fate but what we make for ourselves.

Also from the script:

Bathed in sweat, Sarah sits hunched over the table. Every muscle is shaking. She is gasping. Sarah struggles to breathe, running her hand through her hair which is soaked with sweat, She can escape from the hospital, but she can't escape from the madness which haunts her.

She looks down at the words she has carved on the table, amid the scrawled hearts and bird-droppings. They are: "NO FATE." Something changes in her eyes. She slams her knife down in the table top, embedding it deeply in the words...

Then later:

John and Terminator ponders the message carved into the top of the picnic table. Sarah's knife is still embedded there.

John: "No fate." No fate but what we make. My father told her this... I mean I made him memorize it, up in the future, as a message to her -- Never mind. Okay, the whole thing goes "The future is not set. There is no fate but what we make for ourselves."

These lines become something of a motto in both Terminator 2 and the subsequent movies (e.g. "The future has not been written. There is no fate but what we make for ourselves." is the first line of Terminator 3).

This moment of recognition from John Connor certainly seems to signal a change in the series. At this point, free will and its ability to change things becomes more apparent. Consider shortly afterwards, when Sarah takes John to flee to Mexico. If she had done this, it's very likely the events of the future would have remained as they were.

This time, they exercised free will and actually changed the future (and their own fates).

This is a fascinating concept because, as you say, why was one set of actions to change the future and another wasn't? Now you're onto a greater philosophical question - what is free will and how do we know if we're exercising it? If all of our fate and destiny is laid out in front of us, how do we know if we can change it? If instead of taking Door A, we take Door B, how do we know we were't supposed to take Door B all along?

Ultimately, there are no real answers to these questions. What we do know, however, is that James Cameron certainly intended fate to play its part in the second film (whereas predestination seemed to be his focus in the first). We can tell this in two ways. Firstly, consider this quote from an interview with James Cameron:

Basically, what I did in Terminator 2 is say that everything is meant to be a certain way. At least to that point in time where they're sending somebody back from that future. But can you grab that line of history like it's a rope stretched between two points, and pull it out of the way? If you can pull it just a little bit before it rebounds, and cut it exactly at that moment, then you can change it and go in a different direction. If you do that you get a future that no longer exists at all, except in the memories of the people that are here now.

Secondly, he originally intended the actions in the second film to completely change the future. This was presented in an alternate ending finally included on the DVD release, where Skynet has been destroyed and John Connor is actually a Senator (a transcript can be found here). However, he instead chose a more ambiguous ending, where the future was changed, but only to an extent. He explained this:

But there was a sense that, why tie it up with a bow? If the future is changeable, then the battle is something that has to be fought continuously. And you can't do it with a single stroke. That it's the dualism, the dynamic between good and evil that's eternal.

In other words, although the future can be changed, it can't just be completely and totally changed - instead, it would be subtlety, gently changed into a new direction (which also, rather nicely, allows many more films!).

  • Very well done.
    – CGCampbell
    Feb 13 '15 at 21:32
  • @CGCampbell: Thank you, it's much appreciated. Feb 13 '15 at 21:32
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    Reese tells Sarah that he might be from "one possible future", in which case, there is an element of probability involved. If Skynet and John Connor are possible, then they can send stuff back in time. It's similar to the way time travel is presented in Quantum Leap. In "A Leap for Lisa", Sam leaps into a young Al, and screws things up so bad that there is a 100% chance that Al gets court martialed and never joins the QL project. At that moment, Al is replaced by another observer (played by Roddy MacDowell). Only when Sam is able to lower the chance of Al going to prison does he return. Aug 8 '16 at 19:16

The point of the first movie was simply to prevent Skynet from making a change to the past by killing Sarah before John was born. I doubt Skynet realized that Kyle Reese was actually John's father, and that by sending the T-800 back, it was in fact, setting in motion the very events it was attempting to prevent. (Or it may have understood that fact and been forced to act in order to prevent the paradox.)

In the second, though, Sarah takes an active role in trying to stop Judgement Day. It is more than just stopping the T-1000 sent back for John, as the first move was. Instead, she is intentionally using foreknowledge gained from the T-800 to attempt a change that will affect the future. She partially succeeds and manages to push the actual date of Judgement Day back, but is unable to stop it entirely.

So, the first one wasn't intended to change the future (from the humans' point of view), but just to preserve it.

  • 1
    I guess I don't see why intent matters. Just because the characters weren't actively trying to change something doesn't mean it won't be changed. There is either one set of physical laws being applied (e.g. the Novikov principle), or another (that the past can in fact be altered). But the two movies seem to differ on which set of laws apply. Dec 13 '14 at 4:25
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    @PeteyPabPro why can't the future be malleable, but the first movie just doesn't happen to alter it? Real world example: house keys are made from brass, but most people don't bend the keys enough that they fail to open their locks. Just because something can be changed doesn't mean it must be changed.
    – atk
    Dec 13 '14 at 15:22
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    @atk Two comments 1) the world is chaotic (a la the butterfly effect), so it's essentially impossible that any changes in initial conditions will not result in a changed future, but even aside from that 2) the future in the original Terminator was dependent upon the 1984 events, whereas in Terminator 2 the future would be impossible with the 1995 events. So there is a fundamental difference. Dec 13 '14 at 20:09
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    @PeteyPabPro, 1. Different conditions can result in nearly duplicate or totally differed futures. You seem to be assuming that they must necessarily be totally different, which I continue to question. 2. Was it really dependent upon the '84 events? I contend that (unless there is cannon evidence to the contrary) different, but similar events could have led to skynet and judgment day in the timeline prior to the '84 events. For example, Conner could have had a different father, and the half destroyed picture with Sarah that Kyle carried around could have had this other father until it was...
    – atk
    Dec 13 '14 at 22:26
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    @atk is it really reasonable to think that, for example, the photo would have looked exactly the same way in a totally different version of reality? Or that John Connor really would have been the same leader if he had a different father? The Novikov principle (mentioned above in a comment in the original post) is a much more likely explanation. Dec 14 '14 at 6:23

I think it is very simply that nothing in the first movie that happened would have changed anything in the future? Granted the chips they had from the 1st Terminator play a role in how Skynet started in the second film was linked. Other than that.. but then again it has been years since I've seen these films.

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