In Back To The Future, Marty calls to Doc's house to try to get his help, explaining that he's from the future. Doc flat out refuses to believe him, responding with sarcasm and incredulity, laughing at the notion of a celebrity president of the US, before running out of his house and down to his workshop / garage and slamming the door in Marty's face.

But why? While this might be an appropriate response from your average scatterbrained scientist, Doc had just that very day come up with the idea for time travel! Surely he should be completely open to the idea that someone could visit him from the future, especially with it so fresh in his mind.

  • 56
    Because it's more likely that Marty's a crazy person.
    – Valorum
    Commented Aug 27, 2019 at 7:38
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    Also, the Doc is suffering from concussion and may well be hallucinating...
    – Valorum
    Commented Aug 27, 2019 at 7:40
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    I know that lotteries exist, but I still hang up when someone calls to tell me I won money.
    – Misha R
    Commented Aug 27, 2019 at 15:37
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    Doc had just come up with the idea for the flux capacitor. Did he also immediately realize that it would make time travel possible?
    – jamesdlin
    Commented Aug 27, 2019 at 18:58
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    @MishaR: even if you played at LotteryMaxSuperBonus and someone who tells you they are from LotteryMaxSuperBonus calls you? I understand your point about unsolicited calls but in that case Doc was info time travel and someone claiming to time travel came to him.
    – WoJ
    Commented Aug 28, 2019 at 7:30

3 Answers 3


When Doc finally believes and sees the DeLorean and the real flux capacitor, the first thing he says is, “It works!! I finally invented something that works!”

None of his inventions have been successful before, so he has no reason to believe Marty when Marty opens with the claim that the time machine he came in was invented by Doc.

Also, the second piece of evidence (Doc completely ignores the first piece) Marty tries to use to prove his claim is the photo of him and his brother and sister. Because the future is already changing, his brother has started to fade, which Doc interprets as evidence that the photo is a fake. That’s when he asks who the president is.

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    His attempts at reading Marty's mind were actually pretty good near hits. Commented Aug 27, 2019 at 16:45
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    @MichaelRichardson Perhaps the time machine isn't so much the first of his inventions that works, as it is the first of his inventions to be independently confirmed as working. ;)
    – Steve-O
    Commented Aug 27, 2019 at 17:52
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    @MichaelRichardson I mean, he guessed successfully that Marty was from a great distance (temporally, mind you). His attempt with the newspaper subscription was a complete guess, and his attempt with the coast guard donation was because of Marty's clothes, and was still wrong. I'd not exactly call those "near hits". His assessment of "this damn thing doesn't work at all" was the most accurate statement he made.
    – Cat
    Commented Aug 27, 2019 at 21:22
  • @MichaelRichardson Doc was guessing the whole time; the people in town and his grandparents thought he belonged to the coast guard too... it was a running joke in the movie. They all saw his bright orange vest and concluded sailor.
    – djm
    Commented Nov 20, 2019 at 21:33

Occam's Razor: the simplest solution is usually the correct one.

So what's more reasonable / plausible? Marty is from the future or Marty's is high / crazy or playing an elaborate prank on Doc Brown?

Doc is a man of science; he's skeptical by nature. It's only when Marty shows him hard evidence and relating the story of the flux capacitor does he start believing. A story only Doc knows or so he thought...

In the movie, I also vaguely remember Doc Brown alluding to the kids in town playing pranks on him. So, Doc initially concluded that the kids in town were messing with him again.

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    Not to be a pedant, but I think he's more of an engineer/inventor than a scientist. There's no real hypothesis testing, and by extension no scepticism.
    – Sparhawk
    Commented Aug 28, 2019 at 13:19
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    @Sparhawk That just makes him a different kind of scientist - specifically, the mad kind. Commented Aug 28, 2019 at 13:23
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    @DarrelHoffman : No. A mad scientist proposes a new death ray, publishes, and defends to his death the findings of that paper. A mad engineer actually builds one. Commented Aug 28, 2019 at 15:55
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    @EricTowers The mad scientist hires a couple of mad engineer grad student peons to build the thing for him.
    – GreySage
    Commented Aug 28, 2019 at 20:01
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    A simple engineer/inventor doesn't build a portable cold fusion reactor in his DeLorean... Commented Aug 29, 2019 at 12:37

If I remember correctly, Doc was perfectly willing to believe Marty until he said that Ronald Reagan was US president in 1985. In the 50s, Reagan was just a second-rate actor, as evidenced by the poster for Bedtime for Bonzo at the cinema Marty walks by before meeting Doc. It is this that makes Doc incredulous and sarcastic: "Who is vice-president, then? Jerry Lewis?" (quoted from memory). It isn't until Marty tells Doc how he got his head injury that Doc changes his mind again.

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    That’s not how I remember it. Marty: “Doc. I came here in a time machine that you invented. Now I need your help to get me back to the year 1985.” Doc: “Do you know what this means!? It means that this damned thing [the mind reader] doesn’t work!!” Doc doesn’t believe it at all from the start. He’s just stuck on his disappointment about another invention that doesn’t work. Commented Aug 27, 2019 at 14:53
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    @ToddWilcox I'm not sure that line means he doesn't believe Marty. He's just so focused on the mind reader that he didn't consider the other consequence, that time travel is real.
    – Barmar
    Commented Aug 27, 2019 at 16:48
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    What's interesting about this question is that most presidents in Doc's lifetime were around 50 at their inauguration. The idea that Doc would actually recognize the name of the president 30 years in the future is incredibly unlikely since they would be in their early 20s in the 1950s and would likely not have made a mark in public life yet. Indeed, Reagan's age at his inauguration was the highest ever at the time and the record wasn't broken until Trump.
    – Dancrumb
    Commented Aug 27, 2019 at 19:29
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    @Dancrumb: Yeah, the list of presidents who would have been recognizable 30 years before their term consists of Reagan, Trump, and maybe John Quincy Adams. William Henry Harrison is likely a near miss (he died in office almost exactly 29 years and 6 months after the Battle of Tippecanoe).
    – Micah
    Commented Aug 27, 2019 at 21:13
  • 2
    Kind of raises the question: not counting people excluded by the Constitution, try and think of one person who we could not imagine being president in 30y time. :'(
    – Dancrumb
    Commented Aug 27, 2019 at 21:21

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