Handling the Grandfather Paradox

Time travel stories are maybe my favorite type of science fiction story. However, as I get older I find that I have higher standards for what makes a good time travel story. I realized this after recently reading a the novel Man in the Empty Suit and seeing the film Looper, both of which I think are only so-so time travel stories for reasons I’ll discuss.

(Spoilers for both of those stories below.)

What I mean by “a time travel story” is a story where the use of time travel is integral to the plot and its development, it’s not simple an enabler for a basically different story.

For example, the film Star Trek IV: The Voyage Home is not an instance of what I mean by “time travel story”. Time travel is an enabling plot device, but the story itself is a light comedy driven by a clash of cultures, and the time travel is just a means to get into that situation. Similarly, H.G. Wells’ The Time Machine leaps into the far future, but again it’s just a means to get our hero to a far-off shore, the fact that time travel was used is mostly immaterial to the plot.

To me, a time travel story at least skirts, and realistically has to somehow grapple with, the Grandfather Paradox. Some sequence of events which threatens to break the protagonist’s timeline so that the story you’re reading can’t happen. Paradoxes and the avoidance thereof are part and parcel of the story.

What frustrates me about many time travel stories is that they play fast and loose with what happens when someone changes history, and don’t explain what their model of changing history involves.

For example, consider Looper (2012): I think this film runs into problems because it has some clever scenes it wanted to depict, but those scenes undercut the whole story.

The film takes place in 2044, where Joe (Joseph Gordon-Levitt) is an executioner. Sometime in the future, time travel will be invented, and outlawed, and the mob will use it to send people back to 2044 to be executed. At some point the mob will send the loopers back to be killed by their younger selves, at which point their “loop has been closed” and they’ll be retired with a big payout, which they can enjoy until sometime 30 years hence when they’ll be picked up and sent back for execution. (There are some motivational problems with the story – why would the mob wipe out the loopers 30 years after they retired? – but I found them easy to forgive, and they’re not my concern here.)

The most chilling scene in the whole film is where Joe’s friend Seth (Paul Dano) fails to close his loop, and his future self (Frank Brennan) escapes. The present-day mob captures young Seth and carves a message into his arm to get to a certain address in 15 minutes, which his future self sees as history has been changed. The mob doesn’t want to just kill young Seth since that may change time more than it can handle, but instead they start mutilating him and cutting off his limbs, which his future self experiences as he travels to the site. When he arrives he is killed.

Young Seth is not killed, but he’s obviously maimed and crippled for life (his legs have been amputated, for example, and his nose cut off). It’s a very effective scene when it’s happening, but how can these changes have been significantly less serious than just killing him? Maybe Seth’s future life was largely irrelevant, but if so, why not just kill him? It’s not explained, so it makes the film feel sloppy at one of its best moments.

The crux of the film is that future Joe (Bruce Willis) comes back, and also escapes his execution. He has identified three children, one of whom will grow up to be “the Rainmaker”, the big boss of the mob in the future, and he wants to kill him before he grows up in order to prevent that from happening, and also save his wife from being killed when he is rounded up. He and young Joe have a showdown over the boy who is the future Rainmaker, and young Joe realizes that this very experience may be what turns the kid bad, so he commits suicide before old Joe can kill the kid’s adopted mother, causing old Joe to disappear.

This paradox basically rips the story apart, because it means that none of what happened after old Joe arrived could have happened, and yet it obviously had to happen. (Secondarily, the film fails to show that young Joe’s sacrifice actually prevented the Rainmaker from developing – the film is missing its denouement, which is critical to it being emotionally satisfying.) The story is fundamentally flawed because even by saying that time travel is subject to the many-worlds interpretation wouldn’t have fixed it, because then young Joe killing himself wouldn’t have caused old Joe to disappear, since old Joe came from a different branch of time. So the story ends up as something of a mess, pretending to use time travel in a serious manner but not treating it very seriously.

Man in the Empty Suit, by Sean Ferrell, has similar problems. It has a really neat premise (which is why I bought it): The protagonist invented a time travel device (the “raft”) when he was 19, and every year of his personal time he travels to New York exactly 100 years after his birth (i.e., to the 2070s) to have a party in an old hotel with all of the other birthday incarnations of himself. The main version of the character is 39, and he learns when he arrives that his age-40 version will be killed, and that all the older versions of himself have been covering this up, and expect him to solve the mystery and keep it from happening.

It’s a great idea, but it opens up several expectations which the book really has to meet to work:

  1. Who kills his 40-year-old self, and why?
  2. How can his future selves exist if age 40 was killed?
  3. How can he prevent his own death while still appearing to die?
  4. Why don’t his future selves know what happened and how to prevent it?

The book is filled with loops, in which the main character sees or learns about things which will happen in his future, and then duly makes sure they come to pass when the time comes. But it also has some flat-out paradoxes, the cardinal example being when one of his mid-30 selves breaks his nose, and one of his slightly-older selves changes things so it doesn’t happen. So some of his selves have a broken nose, and others don’t. Also, while there “should” be only about 50 of his selves around the party (since the oldest one we see is 70), there are many more, including many from before he invented the raft, and he has no memory of them having been there.

I think the book is trying to go for a many-worlds interpretation of events, but it’s messily handled since characters seem to have memories of events which never happened to them. And the book eventually fails to work out any of the goals I expected it to meet above. Okay, a many-worlds interpretation would address some of them (although we never learn who killed age 40 or why they did it). So the book ended up being a big disappointment because the messy time travel and lack of a structure for how it worked made everything else much less meaningful or sensical.

I think time travel stories appeal to me in part because getting the pieces to fit together is challenging, and figuring out how they fit is fun. So when a story doesn’t deal with the Grandfather Paradox appropriately – or at least tried to – I find it really frustrating. Dealing with it usually means taking one of the following approaches:

  • There are no paradoxes, because everything gets carefully worked out so that everything happens exactly as it always did, despite the presence of time travellers. This can be very difficult to do, but it’s really satisfying when it happens. The original series of John Byrne’s Next Men comic book did this really well. (The later series tore it all down and is therefore not nearly as interesting.)
  • The shadow history approach: There are no paradoxes, but it seemed like there might be because the characters had an incomplete understanding of what happened in the past. The story is often focused on illuminating those things. (Some stories use time travel to retcon something from an earlier story which didn’t make sense, which is a variant of this approach.)
  • Use the many-worlds interpretation. This is perfectly reasonable, but it also means you can’t have paradoxes: Changes to a character’s past don’t affect the character’s present, because they create a new timeline with a different instance of that character. This takes away the “character gets killed, his future self goes poof” effect that some writers like to use, as in Looper. But you can’t have it both ways. X-Men: Days of Future Past (both the original comic story and the film) use this approach. In the film, Logan goes back from the dystopian future to 1973, creates a new future timeline, and then returns to the present in that timeline. But there’s no evidence that anyone in the present remembers the other timeline, other than what Logan told them in 1973.

A good example of a film that handles the Grandfather Paradox well is the first Back to the Future, which works because it strongly suggests that the paradox could be created, but our hero prevails and manages to fix his timeline (even if some of the details get revised in the process). The first Terminator film takes a subtler approach where everything works out the way it was supposed to.

Looper would have had to sacrifice some of its cool scenes to satisfy me as a time travel story. But Man in the Empty Suit I think could have been pretty satisfying if it had stuck close to its original premise and not brought in all the paradoxes – or better, come up with a framework where the paradoxes either aren’t what they seem to be, or are explained due to events the hero wasn’t originally aware of. I kept hoping there was an explanation for how age 40 was killed, yet the character survived. But the writer wanted the story to go in a substantially different direction, which wasn’t the story I wanted to read, and wasn’t the story I felt I’d been promised by the premise.

Too bad, because it started off so cool.

4 thoughts on “Handling the Grandfather Paradox”

  1. Looper is actually more complicated than that, since Old Joe remembers killing another Old Joe, but changes his own past by escaping. The implications of what can happen aren’t explored at all – although one possible implication is that the Looper universe doesn’t have a single timeline.

  2. Did you ever read David Gerrold’s The Man Who Folded Himself? I just reread it a few months ago after not having read it for many years. I think Gerrold works hard to explore the different possibilities and permutations of both time travel and creating parallel versions of yourself via time travel but in many ways it’s very self-conscious about what it’s trying to do as a novel.

  3. As an example of how trying to be rigorous about this can make things difficult, consider “Primer”. They’ve got a fairly normal multiple-timelines version of time travel, but after the first couple of trips, things get progressively more and more messy, and some people really found it difficult to understand what’s going on as a result. Of course, some uber-nerds have spent the time to create a map of all the timelines in the movie, to try to untangle things.

    And the whole *point* of the movie isn’t so much time travel as it is the dynamics of the friendship between the two main characters, and their different reactions to the power that the machine represents. I really wish it was a little better-made, because the god-awful sound mix, and the lighting issues in some scenes, don’t help with the whole “wait, what just happened?” aspect of things.

  4. I agree that in Avengers Endgame they didn’t explain their approach to time travel. It seems unclear if they intend to clear it up in future films and/or tv shows.

    What do you recommend beyond Back to the Future and Terminator? What did you think of the time-travel stuff in Harry Potter and Prisoner of Azkaban (or in Harry Potter and the Methods of Rationality, which is a fan work but one I endorse)? Have you read Rant by Chuck Palahniuk?

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