Consistent Time-Travel Movies: A Quasi-Philosophical Love Letter (UNLOCKED)

Most time travel movies rest on deeply confused models of past-future-past causation. So let's take a moment to appreciate the gems that don't. You can, I promise, learn to love causal loops.

In the essay two Sundays ago, I went through some of the academic literature on time travel paradoxes. If you think philosophy needs to earn its keep by being relevant to the real world, and you’ve never been invited on a DeLorean ride to the nineteenth century, you might find all this logic-chopping about what imaginary time travelers would or wouldn’t be able to do—or whether the whole idea of time travel makes sense in the first place—a little much.

And I get that reaction, truly. There’s a reason the vast majority of what I’ve covered here has circled around a few subjects—most obviously moral and political philosophy, free will and determinism, and philosophy of religion—of far more general human interest.

Granted, the last item on that list has to do with debates about entities that I and many people reading would judge to be imaginary, but at least that one is a live controversy. 84% of the population of the world has some sort of religious affiliation, and even if “has some sort of religious affiliation” is no guarantee of actually believing much of anything, there’s at least a significant percentage within that overwhelming majority of the human population that truly and deeply believes. No one is organizing their emotional life around a deeply held belief that one day Doc Brown is going to drop by in the DeLorean and whisk them off to 1885.

So all I can say in defense of doing two entries on time travel is that time travel is fun. At least in my case, it was one of the first things I ever thought about—“could you change the past, does that even make sense?”—that helped me think in a ‘philosophical’ way, reasoning about abstract possibilities, long before I’d ever stepped into a philosophy classroom or so much as heard of Descartes or Kant or Bertrand Russell. I suspect I’m not alone in that either, for the mundane reason that this particular bundle of head-spinning conceptual questions comes up in a lot of movies.

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Looper is not, I think, a great movie qua movie. And it scores very low for “well-thought-out time travel rules”. But there’s a scene that charmed me enough to stick in my memory a decade after the one and only time I watched it, in a movie theater in South Florida in 2012.

Joseph Gordon-Levitt meets Bruce Willis, who’s playing Old Joseph Gordon-Levitt from the Future, in a diner. They order steak and eggs and black coffee—the same order, he hasn’t changed—and they do some action-movie banter and they have this exchange:

Gordon-Levitt: “So you’ve done all this already? As me?”

Willis: “I don’t want to talk about time travel shit. Because if we start talking about it, then we’re going to be here all day, talking about it, making diagrams with straws…”

Spoken like a man who’s watched a lot of time travel movies.

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As a kid, I absolutely loved Back to the Future. I can remember being nine years old and driving to the movie theater with my dad, who I’d been begging to take me to see Back to the Future II, and being over the moon when we got there and he finally revealed that, yep, that’s what we were there to see.

In my late twenties, I watched the first installment in the trilogy for what was at that point the first time in many years. I was studying for my Ph.D. in Philosophy at the University of Miami, and I was watching with a bunch of other grad students. I was, I think, more than a little high. And the total absurdity of the time travel rules hit me with great force. I don’t remember if I was obnoxious enough to actually pause the DVD to say all of this or if I at least had the decency to wait until it was over, but I can remember ranting about the family photo Michael J. Fox kept looking at throughout the movie.

If you haven’t seen Back to the Future lately—and by the way, since talking about the plots of movies without “spoilers” is hard enough for the kind of movies where the flow of causation only goes in the traditional present-to-future direction, and would totally defeat the point for my purposes here, consider this a generalized “spoiler warning” for not only Back to the Future but every other movie discussed in today’s essay—teenage Michael J. Fox goes back to 1955. Every time he does something that brings his teenage parents further apart, the family photo starts to fade. Every time he does something that brings them closer together, it gets clearer again. There’s a point where he’s looking at the photo and about half of his older brother is there—the left half, I think—and I really wanted to know what would happen if he stopped interfering in the past at that exact moment. If he’d somehow solved his transportation problem and gone back to 1985 right then, would he be greeted by half of his brother?

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Fast forward several years, and my then-wife and I were living in South Korea. (She was still finishing her Ph.D. at Miami long distance, and I was teaching at Yonsei University.) Jennifer had somehow managed to grow up in the United States but never see Back to the Future, which I found appalling, and we watched it on a laptop computer in our apartment in suburban Seoul.

This time around, I was watching it through far less grad-student-y eyes, and I got caught up again in the dream-like atmosphere. The totally-incoherent-if-taken-seriously time travel rules didn’t bother me. The movie worked for me as the weird wonderful 1980s fairy tale it is.

All of which is to say:

There are great movies that don’t survive the “making diagrams with straws while you and your friends are out at the diner by the movie theater” treatment. And that’s fine. But the activity being gently mocked in the Bruce Willis line in Looper is itself part of the joy of watching time travel movies and I want to take a minute here to appreciate the ones that do pass the test.

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In the essay two Sundays ago, I argued—building on a classic paper by David Lewis—that there’s nothing especially paradoxical about the “Grandfather Paradox” or similar time-travel head-scratchers. If you could travel backwards in time, “could” you kill your grandfather? Or kill Hitler before his rise to power? You “could" in the sense that anyone who doesn’t successfully carry out an assassination “could have” done so—that is to say, fiddle with the starting conditions a little, like giving you a clearer shot or having Hitler not realize what was going on for another couple of seconds—and voila, you succeeded. It’s just that we know that you didn’t succeed because if you had (in the grandfather case) you wouldn’t have existed in the first place or (in the Hitler case) you wouldn’t have been motivated to do it in the first place, because there would be no historical record of Hitler’s crimes as Führer for you to be motivated to prevent. But the only difference between that and any other case of an assassination attempt that didn’t succeed but could have is that, if you think about it, you can extrapolate the fact of the failure in advance—not because of some deep metaphysical truth but just because the failure already happened and thus already played whatever role it was going to play in the cause-and-effect sequence leading up to the present (and hence to the attempt itself).

That’s confusing when you first bust out the straws and try to think it through. And in the essay, following the lead of Lewis and most other philosophers who have written about this, I focused on issues about possibility and necessity. But in my experience the deeper block to thinking clearly about this stuff that a lot of people struggle to get past is the “already happened” part. Questions like, “OK, but what guarantee is there that I won’t succeed in killing Young Grandpa? What would stop me?” reveal that a lot of people trying to puzzle their way through this are in the grips of what the Australian philosopher Nicholas J.J. Smith, in his excellent and excellently titled paper Bananas Enough for Time Travel, calls “the Second Time Around fallacy.”

God knows a lot of Hollywood screenwriters seem to be in the grips of that particular fallacy. We’ll get to it. But first let’s look at a movie that avoids it.

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I rewatched Terminator around the same time as Back to the Future. They came out around the same time (1984 and 1985) and if I were a different kind of academic I’d probably have something to say about what both films say about the cultural preoccupations of Reagan-era America—most obviously, both of them are about preventing threats to future motherhood.

Of course, in Back to the Future the threat to future motherhood is that the future mother will, like, kiss the wrong boy at prom. In Terminator, it’s that she’s going to be iced by a killer robot going through the phone book killing everyone with her name just to make sure she’s dead.

Where Back to the Future is a dreamy fairy tale, Terminator is a Western. A lot of the beginning of the movie is about the two rival gunfighters getting into town and sizing each other up.¹

But, like Back to the Future, there’s a photograph that says a lot about how time time travel works in this universe. Hamilton’s character, Sarah Connor, is being saved from the killer robot by Kyle Reese, sent back in time for the purpose by Sarah’s future son John Connor. In Kyle and Sarah’s brief time together before he dies, he becomes John’s father—and tells her that he fell in love with her in the future, on the basis of a photograph given to him by John.²

At the end of the movie, an already pregnant Sarah is driving through Mexico and she stops at a gas station. There are chickens wandering around and a couple of piñatas dangling above the pumps and the gas station attendant is wearing a sombrero, since James Cameron is apparently worried that viewers otherwise won’t be able to put it together that this is happening in Mexico. And, yeah, I’m making fun of this scene, but I also love it, both because in a cheesy 1980s action-flick way there’s a poetry to it that still works for me—“there’s a storm coming”—and because it’s a final reminder of the way the whole plot of Terminator is an elegantly-constructed causal loop.

A Mexican kid runs up and takes a snapshot without asking, and then offers to sell it to her for “five American dollars” and she bargains him down to four—and that, of course, is The Photograph. This one’s not going to fade and re-emerge as the timeline is messed with because Cameron and his co-writers seem to have intuited at the time—even if they forgot when it came time to write the sequels—that “messing with the timeline” is an incoherent notion.

This is Nicholas J.J. Smith’s point about “the Second Time Around fallacy”. It’s one I remember putting together as a nerdy adolescent or teenager—I don’t remember exactly—probably thinking about some time travel movie or another and realizing what had been bothering me about the plot. If you’re traveling back into the actual past of our universe, the idea that you’ll do something in the past that changes the present is incoherent, because your trip into the past already happened and already had whatever impact it was going to have on the present.

When you ask, “OK, but what would stop me from killing Hitler if I traveled back to 1932?” you’re talking as if there’s a “rough draft” of 1932 that doesn’t include your time-traveling assassin self and a “revised draft” that does but no matter how you slice it, whether there are many timelines or just one, that doesn’t work. If you’re talking about an actual trip back to the 1932 of our universe, then that already happened and you were stopped by whatever mundane thing happened to stop you, like any regular non-time-travel foiled assassin. If you’re somehow traveling to the 1932 of an alternate reality where you assassinated Hitler in 1932, then that’s probably a lucky break for the alternate reality version of some of my distant cousins in 1933-45, but it won’t help their counterparts in our timeline.

The honor roll of Hollywood movies that get this very basic conceptual point right—if you’re traveling back to the past that had a causal impact on the present, your trip by definition already happened and already had whatever causal impact it was going to have—is very short. Off the top of my head, the first Terminator, 12 Monkeys, weirdly enough Harry Potter and the Prisoner of Azkaban—the time travel part is a relatively small part of the plot, but it’s a well-executed Terminator-style causal loop—Predestination³, and (really!) Bill and Ted’s Excellent Adventure and Bill and Ted’s Bogus Journey. Probably also some movies I haven’t seen and almost certainly a few I have seen and don’t remember that people are going to remind me of in the comments. That’s how this goes.

And look.

I get why it’s so rare. It can’t all be chalked up to muddleheaded screenwriters or their muddleheaded bosses—although, like, let’s also not pretend that’s not a factor at all. There are all sorts of dramatic possibilities that are closed off by actually well-thought-out, internally consistent time travel. You don’t get to do the trope where you get back to 2023 and everything’s changed. There are certain things that, at least if the viewers are expected to realize that this is a consistent time travel story, aren’t gonna have much in the way of dramatic stakes. (If you send your character to 1932 to kill Hitler, and everyone realizes we’re dealing with internally consistent one-timeline time travel, there might be drama about what happen to the assassins, but even an audience of ardent Nazis won’t fret too much about the Führer.) That all makes sense. Even if you have thought about it, if you make the not unreasonable calculation that the audience hasn’t (and the portion that has doesn’t really care), why straitjacket the plot?

All I can say is that I’ve grown to love the few actually consistent time travel stories and you might find that you do too. The most important twentieth-century philosopher non-academics have never heard of, W.V.O. Quine, has a memorable phrase in one of his papers about how, above and beyond any feeling that a simpler theory of the universe is more likely to be true, there’s a purely aesthetic appeal to ridding your picture of reality of the unnecessary clutter—a “taste for desert landscapes”.

And there might be a (very rough) parallel there to the taste you can develop for the literary fatalism and the clockwork intricacy of plot construction that tend to crop up when writers set themselves the task of telling time travel stories that actually make sense. I can turn off that part of my brain and watch Back to the Future—or, hell, Hot Tub Time Machine—with great joy. But I wish Hollywood would give us more time travel stories that we could watch with the mental lights turned on all the way through the end credits.

1. While we’re doing genre assessments, it’s maybe worth noting that cyberpunk was just starting to come into existence—Bladerunner helped give birth to that aesthetic a couple years earlier, and William Gibson’s novel Neuromancer came out the same years as Terminator—and, while Terminator is certainly not cyberpunk, the night club where Linda Hamilton goes to hide out from Arnold Schwarzenegger is actually called “Tech Noir.”

2. Presumably John knew this story when he gave Kyle a picture of his mom, which makes you wonder what was going through John’s head, but I suppose when it comes to assuring your own future existence, you get over it and do what you need to do.

3. As a movie, Predestination is just OK. But the Robert Heinlein story it’s based on—‘—All You Zombies—’—is delightful. And while we’re doing prose fiction, big shoutout to Ted Chiang’s The Merchant at the Alchemist’s Gate, which manages to perfectly combine the forms of “logically consistent time travel story” with “fatalistic Middle Eastern fable”.