Peeled banana illustration on green background

Time Travel 2: This time it’s serious

Second YEAR Philosophy PHD STUDENT LIV on what stops time travellers from changing the past

Welcome back to another blog post all about time travel. This time I’m going to be talking about coincidences. If you read my last blog post (if not I would seriously recommend reading it before this one: A (very) short introduction to time travel and film) you will remember we spent most of it talking about some crucial elements of consistent time travel. We noted that, in order to maintain a nice consistent time travel story, time travellers cannot change the past (sorry all you Back To The Future fans).

But what happens if a time traveller tries to change the past? What happens if a time traveller stands in front of baby Madonna and tries to murder her? Ultimately, what stops them from changing the past? In this short blog post I will hopefully shed some light on this question. So without further adieu let’s get into it…

What a coincidence…

It’s hard to believe in coincidence, but it’s even harder to believe in anything else.

John Green, “Will Grayson, Will Grayson”

There are two things which define Louise as a person. First, she is a time traveller who has been on many time travel journeys over the years. Second, she hates Madonna, believing that the world would be better off if she never existed. One day Louise makes the tenacious decision to go back in time and kill the baby Madonna (so before she grows up to become the pop icon we know and love today). Louise has planned the murder perfectly, she knows the exact whereabouts of baby Madonna and has been practicing at the shooting range every day leading up to the journey. The day arrives, Louise steps into her time machine and heads back to 1960. She steps out of the time machine and comes face to face with a 2-year old Madonna. Louise pulls out her gun and fires at Madonna. What happens next?

As we’ve already established Louise definitely cannot successfully kill the baby Madonna, since we know that Madonna lived past 1960. If Louise was successful then Madonna would have both been alive to release some of the greatest songs ever made and not been alive. This is a contradiction and therefore impossible – something cannot both be A and notA at the same time. So what does happen? If Louise cannot kill baby Madonna something must happen to prevent her from doing so. Enter coincidences.

David Lewis (famous philosopher and all-round great guy) suggests that some ‘commonplace reason’ will prevent a time traveller from changing the past. This could be a gust of wind, a noise distracts them or they slip on a banana peel. The take-home is, something has to happen in order to ensure the failure of the successful exercise of the action. These events are now said to be coincidences.

Oh my gosh, that is such a coincidence

We all use the word coincidence a lot but in philosophy, it holds a little more weight. A coincidence in philosophy is an event or events which seem to have no apparent cause. They are said to be extremely unlikely (probability nearing zero), but nonetheless possible. Hence, it is not logically impossible for a time traveller to slip on a banana peel at the exact moment they were meant to shoot baby Madonna, or for a gust of wind to blow the bullet off track. Basically, weird stuff happens all the time, things that we cannot explain, which seems to have no apparent cause, so why can’t weird stuff happen in time travel scenarios as well?

The presence of these ‘coincidences’ within time travel scenarios has caused some to become sceptical of time travel. Not so much of it’s possibility but of it’s probability. As I mentioned above, coincidences are, by definition, unlikely occurrences. So, if time travel were to entail these sorts of coincidences surely that makes time travel an unlikely occurrence as well? Let’s say Louise failed to kill baby Madonna the first time, she slipped on a banana skin. However, she really does not like Madonna, so gets up and tries again, and again, and again. She keeps trying. Do these coincidences keep happening? Well, yes. So maybe it doesn’t seem too unlikely that it happens once, but repeated coincidences might be a little hard to swallow. I won’t go into this too much here, because it’s a pretty hot topic within the time travel literature. Just something to think about…

Thank you for joining me for the latest instalment of the time travel blogs. I’ll probably do another one soon as there’s so much left to talk about. I’m really only scratching the surface. If you’re at all interested in any of this and want to read more stuff on time travel, please just email me: ocoombes [at]

Have a great week!

About Liv

Philosophy PhD student Liv is the Philosophy Social Media Ambassador (Research Focus) at the University of Edinburgh. Keep an eye on the Philosophy at Edinburgh Twitter account @UoE_Philosophy for more updates from Liv.

This post was originally published on PPLS Student Blogs
Time Travel 2: This time it’s serious | Student Blogs

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