Why Doc Brown should secretly destroy the DeLorean
It can be used for evil, sometimes unwittingly. And it is a proof to the bad actors that one can change the past.
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If I could turn back time
If I could find a way
I'd take back those words that have hurt you
And you'd stay
—Cher
Time travel holds a strange power over the imagination. The idea of being able to go back and fix something—right a wrong, pursue a lost love—is nearly irresistible. It is no surprise then that Back to the Future has remained so iconic. It taps directly into this deep human fantasy: the fantasy of control over time itself.
But here is the catch. If you could really change the past, you’d be stepping into a minefield (and luckily you can't—I'll explain in a bit). Every choice you make could detonate the lives of millions—possibly even your own. That’s not just hypothetical. That’s what nearly happens to Marty McFly when he almost erases himself and his siblings from existence by meddling with his parents’ love story.
And it’s not just personal relationships at stake. In Back to the Future Part II, Biff uses the time machine to make himself rich and powerful—and Hill Valley ends up looking like a cross between a casino and a post-apocalyptic wasteland.
Doc Brown eventually realizes the danger. He warns Marty about the chaos unleashed by altering the past. What he doesn’t quite realize is just how deep that danger goes. And that’s what this post is about: why the DeLorean doesn’t just need to be parked. It needs to be destroyed—secretly, and completely.
The Grandfather Paradox
The problem of time travelers changing the past is something confined to the fictional universe of the movie (and that is lucky for us, because there are many downsides to changing the past, even with the best of intentions). Why exactly is that? The first reason is metaphysical. And it has a name: the grandfather paradox.
Let’s walk through the classic version. Marty wants to make sure his grandfather never meets his grandmother. So he travels back in time with a plan to kill his grandfather. Suppose he finds him as a teenager, completely alone and defenseless. Can he go through with it?
No—because if he did, his grandfather wouldn’t have fathered Marty’s dad, and therefore Marty would never have been born. And if Marty was never born, he couldn’t have gone back to kill his grandfather. To suggest otherwise would be a contradiction. As philosopher David Lewis puts it:
“Tim cannot kill Grandfather. Grandfather lived, so to kill him would be to change the past… [If] Tim does kill Grandfather in 1921, then he both does and does not.”²
Time travel to the past, at least if it allows you to change anything, doesn’t just cause problems—it’s logically impossible. It collapses under its own weight.
Still, in the fictional world of Back to the Future, people manage to change the past all the time. So what’s going on there? And why do the moral downsides of time travel outweigh the upsides due to the complexity of changing the past?
The Sports Almanac Loophole (That Isn’t)
Let’s unpack Biff’s infamous sports almanac scam to illustrate the issue. In Back to the Future, Part II, old man Biff steals the DeLorean and gives his younger self a book filled with future sports scores. Young Biff uses it to place bets and become a corrupt tycoon. So far, so bad.
But there is a deeper problem. Where did the almanac come from? The book itself has no clear origin. It’s passed from old Biff to young Biff, who grows up to become old Biff, who gives it to young Biff... and so on.
This is a causal loop that violates the basic principle of causality. And if you look closely, it still leads to contradiction.
Either young Biff has the almanac before old Biff travels back in time—impossible—or he doesn’t, in which case there’s no reason for old Biff to travel back and give it to him. The loop doesn’t close. The narrative breaks.
The deeper you dig into time travel that changes the past, the more you find logical sinkholes. And once you fall in, it’s hard to climb back out.
Time Travel Is a Weapon
Even if we suspend disbelief and assume time travel to the past were possible, the moral risks would be astronomical. A time machine wouldn’t just be a tool. It would be the most powerful weapon ever created.
Imagine a world where a group of Nazis, bitter over their defeat, build a time machine. One of them, Ludwig, goes back to 1944 and warns the high command of the upcoming Allied invasion. History gets rewritten. The Axis wins the war. A single intervention, done at the right time, could undo the victories of democracy, human rights, and basic freedom.
Time travel can also be used for good. Marty’s intervention in his parents’ romance makes his dad more confident and his family better off. But good outcomes are not enough to justify the danger.
Why Destroy the DeLorean?
So what should be done? The moral principle here is simple: it is more important to prevent harm than to positively benefit others. Doctors follow this rule every day. They prioritize saving lives over cosmetic improvements, for instance.
Philosophers Gerald Harrison and Julia Tanner capture this well:
“There is an interesting asymmetry between preventing someone coming to harm, and benefiting someone. Intuitively, it is far more important to prevent causing and/or allowing harm to befall others than it is to positively benefit others.”³
The DeLorean, like a scalpel, can be used to heal or to harm. But the potential for harm vastly outweighs the chance of benefit. And because our duty not to harm is stronger than our duty to help, Doc Brown is morally obligated to destroy it. But that’s not the only reason.
Even Good Intentions Can Backfire
Let’s say Doc Brown really does have the best of intentions. He plans to use the time machine responsibly. Maybe just one trip—to stop a tragedy, save a life, prevent a war.
Sounds noble, right? That’s exactly the mistake made by Chakotay in Star Trek: Voyager. In the episode “Year of Hell,” he tries to erase a comet to prevent conflict. Seems like a simple fix. But it turns out that comet sparked the evolution of life across fifty light years. His tweak to history nearly destroys thousands of civilizations.⁴ The past is tangled. Causes and effects stretch across time in ways no one person can fully understand.
Even something as basic as a peanut butter and jelly sandwich illustrates the problem. You may know how to put one together—but you probably don’t know how to grow the wheat, process the jelly, or manufacture the rubber tires on the tractor that harvests the peanuts.⁶
That’s the insight behind Leonard Read’s classic essay “I, Pencil”: no single person knows how to make even the simplest things on their own.⁶ Our knowledge is socially distributed, as Friedrich Hayek explained.⁵
If we can’t even fully understand sandwiches, what makes us think we can responsibly rewrite the timeline of civilization?
Why Doc Brown Must Destroy It Secretly
So let us pretend Doc agrees: the DeLorean must go. Someone may object: why not just dismantle it and move on?
Because even evidence that time travel is possible can be dangerous. Engineers call it proof-of-concept—a working prototype that shows an idea is more than a theory. Remember the scene at the Twin Pines Mall? Doc sends his dog Einstein one minute into the future. It works. Marty sees it happen. Doc explains the flux capacitor. It’s not just an idea anymore—it’s a demonstrated reality.⁷
That proof-of-concept is enough to inspire others. If the footage of that experiment, or even Doc’s blueprints, fell into the wrong hands, it could jumpstart new attempts to build a time machine. Once you prove something can be done, someone will try to do it again.
That’s why Doc’s duty doesn’t end with destroying the car. He has to wipe out all traces: the video, the notes, the knowledge itself. Because even the idea of time travel is too dangerous to let linger.
Conclusion
Doc Brown is a hero. But part of what makes him heroic is that he understands the gravity of what he’s built. The DeLorean is more than a machine. It’s a potential catastrophe with gull-wing doors.
Time travel may look like fun on the surface. It is different in practice within the Back to the Future Universe—riddled with contradictions, moral hazards, and irreversible consequences. So, the right move in this case is clear: destroy the DeLorean, erase the evidence, and walk away. Because the past, like a fragile ecosystem, shouldn’t be tampered with—no matter how noble the intent.
References
Jimmy Alfonso Licon (2015). The Time Shuffling Machine and Metaphysical Fatalism, Think 14 (41): 57–68.
David Lewis (1976). Paradoxes of Time Travel, American Philosophical Quarterly 13 (2): 145–152, p. 148.
Gerald Harrison & Julia Tanner (2011). Better Not to Have Children, Think 10 (27): 113–121, p. 18.
Star Trek: Voyager (1997). “Year of Hell,” Parts I & II.
F. A. Hayek (1945). The Use of Knowledge in Society, American Economic Review 35 (4): 519–530.
Leonard Read (1964). “I, Pencil,” in The Case for the Free Market, FEE, 136–143.
Back to the Future (1985). Universal Pictures.
Apparently all the rules of physics are valid in reverse. Consider that time moves forward but what's happening is the past in reverse. So the universe reverses as time moves forward. Note that if the universe stops reversing and starts moving forward again then it does not move forward exactly as it did last time as the universe is chaotic and the uncertainty principle means you can't replicate the starting conditions perfectly. Now you would have to figure a way to smuggle yourself unchanged as the universe reverses. If you did all this the grandfather paradox would not apply. Even if you didn't murder him you would never be born anyway as human creation is also a chaotic process so no exact same human being would be born as the universe moves forward again. Essentially you would destroy each person as you reverse past their date of birth.
About the ethics of time travel in the past, it seems to me that your thought is as follows. Preventing harm is morally preferable to helping, and since changing the past, for example righting a wrong, might carry all sorts of unforseen consequences that might cause harm to present and future people, then time travel or 'back-in-time action' is to be avoided on moral grounds.
Just wondering, but, isn't this the very nature of action (or non action, which is a kind of action)?
It might look like the risk is to break something that's working in the present or make worse off lives that are happy in the present by going back and triggering an unwanted change.
But, if time can be reversed those situations and those lives, from the point of view of the past, are just possibilities not real situations or real lives, not unlike future situations and future lives in relation to present action. There will always be consequences, intended and unintended, and acting for the best despite this might be all that's left for moral agents to do.
Or, perhaps, it's just that I'm trying to come up with a good excuse not to destroy the time machine (silently or not) because if it was in my hands I don't think I'd have the moral guts to go ahead and do the right thing.