A paradox of time travel featuring Bootstraps, Beethoven and Black Sabbath

Gautham Shenoy July 22, 2016 9 min


Time Travel and the rules of common logic don’t often agree with each other, with its fair share of tangled timelines, never-ending loops, parallel universes and paradoxes. In this week’s post, we look at one such interesting and much-explored paradox.

So, there’s this man. He time travels to the future and is witness to the end of the world, brought about by a metallic man. Intending to warn the human race, he travels back in time. Unfortunately for him, on his return journey, he gets trapped in a magnetic field and is turned to steel. On reaching his proper time frame, he tries to warn people. But nobody believes him. Instead he is mocked. Until he gets angry, and in his rage starts wreaking havoc on the human race, having his revenge on the world for ignoring him – his heavy boots of lead, filling his victims with dread, as they run as fast as they can – thus himself bringing about the end of the world that he saw when he time travelled into the future.

The question then is, would the end of the world have happened if he hadn’t travelled to the future in the first place? Witnessed the destruction – by himself as it turned out – and travelled back in time to warn people? What’s the cause, and which is the effect? Welcome to the Bootstrap Paradox.

Time’s arrow, you see, isn’t straight or linear and neither does it go only in one direction. As that most well-travelled of time travelers, Doctor Who, from the BBC’s long-running sci-fi series, so eloquently articulated on the nature of Time…

Doctor Who

Time Travel is a recurring theme and plot device in science fiction, with its fair share of paradoxes and tangled timelines. In this post, we look at just one of them, the Bootstrap Paradox. Bootstrapping is a term we’ve heard so often especially in the context of start-ups to refer to businesses that ‘bootstrap’ i.e. use their own internal resources and with no external financial support, self-contained. The term is derived from the phrase, “to pull oneself over a fence by one’s bootstraps”. Yes, a seemingly impossible task. Imagine trying to lift yourself up by tugging at your shoe laces.

In science fiction though, a Bootstrap Paradox – also known as a causal loop – is said to exist or occur when a sequence of events in which an event is among the causes of another event, which in turn is among the causes of the first-mentioned event. Simply put, an effect is its own cause, back and forth in time, in a loop. If it sounds a bit confusing, that’s because it is. This is compounded by the fact that the rules of time travel and don’t get along very well with the rules of common logic. But it all falls into place when you look at the actual instances of it. Like asking, ‘who really composed Beethoven’s fifth?


Here’s how the guitar-playing, time-travelling Doctor Who explains the Bootstrap Paradox. “So there’s this man. He has a time machine. Another thing he has is a passion for the works of Ludwig van Beethoven. And one day he thinks, what’s the point of having a time machine if you don’t get to meet your heroes? So off he goes to eighteenth century Germany. But he can’t find Beethoven anywhere. No one’s heard of him, not even his family has any idea who the time traveller is talking about. Beethoven literally doesn’t exist! The time traveller panics!! He can’t bear the thought of a world without the music of Beethoven. Luckily he’d brought all of his Beethoven sheet music for Ludwig to sign. So he copies out all the concertos, and the symphonies and he gets them published in order. He becomes ‘Beethoven’. And history continues with barely a feather ruffled. But my question is this. Who put those notes and phrases together? Who really composed Beethoven’s Fifth?”

Da da da DAH!
Da da da DAH!!

After that very brief musical interlude, let’s turn to the awesome Terminator series that we’re all familiar with (am not including the muddled mess that was Genisys). There’s two great entangled instances of the Bootstrap Paradox that happen in just the first two movies.

1. Skynet sends the T-800 Model 101 (bad Arnie) back in time to kill Sarah Connor to prevent John Connor from being born. But it is exactly this act that leads to the creation of Skynet itself. Because the damaged CPU and the right arm of the Terminator is recovered by Cyberdyne Systems and becomes the basis for their work on Skynet, which in the future sends the T-800 Model 101 (bad Arnie) back in time to kill Sarah Connor….

2. John Connor sends Kyle Reese back to the past to protect his mother, Sarah Connor from the Terminator. Kyle Reese and Sarah Connor fall in love and have a child, which grows up to become John Connor who in the future sends Kyle Reese back to the past to protect….

Now that you’ve got the hang of the Bootstrap Paradox, it’s time (bad pun intended) to look at the short story that had a direct bearing on the nomenclature of this paradox. By His Bootstraps by Robert Heinlein (writing as Anson MacDonald), the first instance of this paradox in fiction. A college student, Joe, is transported to the future by time-travelling versions of his future self. At one point he meets a much older future version of himself who sends Joe back in time, which starts the whole process all over again. A notebook plays a key role in this story. A book that Joe finds, which he later realises he himself wrote, by copying out his own copy line by line.

astounding bootstraps

As with Beethoven’s 5th, the question becomes, ‘but who wrote the original? Where do the origins of that notebook lie?’ Well, in this particular paradox, faced as we are with a chicken-and-egg situation and in which the looping sequence of events has no clear beginning, it is futile to look for ‘origins’. It makes sense then, to look at Time not as a straight line, but as a circle, with no beginning no end, with events playing out in an endless loop. A causal loop, which is what the Bootstrap Paradox is, doesn’t ‘explain’ itself, it simply is. Whatever has happened, was meant to happen. And will happen again. Everything is predestined. Que sera sera. So much for free will.

Apart from By His Bootstraps, Robert Heinlein – one of the big three of the Golden Age of Science Fiction, along with Arthur C Clarke and Isaac Asimov – also wrote another classic story which typifies this paradox, All you Zombies. No, it doesn’t have zombies as we know them today. But what it does have is a mind-bending oh-wow how-did-that-happen depiction of the Bootstrap Paradox which you can watch – instead of read – thanks to the very faithful adaptation into the 2014 movie Predestination, starring Ethan Hawke as a time travelling agent. To give a summary would be to give away the best part of the movie. Those amongst you who have watched it will know what I’m talking of. For the ones who haven’t I suggest you put it on top of your Must-Watch list, you won’t be disappointed.

Another recent sci-fi movie that cleverly explores this paradox is Time Lapse, about three friends who discover a mysterious machine that takes pictures of things exactly 24 hours into the future, causing some seriously interesting situations and equally interesting causal loops. But the big daddy of complex loops which hints a lot at the Bootstrap Paradox and one that rounds up this week’s list of three great must-watch movies, is Primer. An extremely well-scripted, yet low budget indie movie, completed within $7,000, about two engineers who accidentally discover a means to time travel. After that things get really really complicated.


Christopher Nolan’s Interstellar. The sci-fi comedy, Bill & Ted’s Excellent Adventure. Back to the Future. The Time Traveller’s Wife. The 1971 romantic sci-fi drama, Somewhere in Time, adapted from the novel Bid Time Return by Richard Matheson. Terry Gilliam’s 12 Monkeys starring Bruce Willis. All of these exhibit the Bootstrap Paradox in one way or the other. Check them out to see if you can spot the paradox!

A personal favourite of mine, and one that hinges completely on the Bootstrap Paradox, is Michael Moorcock’s Behold The Man, which packs a lot of punch in a few pages. It’s a tale of a man who travels from the year 1970 in a time machine to 28 AD, where he hopes to meet the historical Jesus of Nazareth. But since we’ve seen now what the Bootstrap Paradox is and ultimately leads to, it’s not difficult to guess what happens next. But as Thomas M. Disch, who we bumped into in the first post of this series, said about why we should read Behold The Man, “…about a Time Traveler questing for the historical Jesus is involved in a case of mistaken identities. The point isn’t What Happens Next because the reader is assumed to be able to foresee that. The point is, rather, how seamlessly the modern version of the myth can be made to overlay the gospel (and so, inevitable) version. To a large degree, therefore, the point is the author’s wit, his grace, and his depth. In a word, style.”

A personal favourite of mine, and one that hinges on the Bootstrap Paradox, is Michael Moorcock’s Behold The Man. It’s a tale of a man who travels from the year 1970 to 28 AD, where he hopes to meet the historical Jesus of Nazareth. But since we’ve seen now what the Bootstrap Paradox is and ultimately leads to, it’s not difficult to guess what happens next.

One last thing before I bid you goodbye until next week. The Bootstrap Paradox, a causal loop, is not to be confused with a Time Loop. While the former is unchanging and self-originating, time loops on the other hand, are constantly resetting. But that is a story for another day.

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P.S.: The story that we began this post with, sounds like the plot of a science fiction novel, doesn’t it? Well. Science fiction, yes. Novel, no. This is the story/plot of the classic Black Sabbath song, Iron Man (which as you can see has nothing to do with Tony Stark).