A (very) short introduction to time travel and film

Happy Halloween everyone, I hope everyone’s has had or is having a spook-filled week. My plan for this evening is to watch The Exorcist for the first time and go to bed before 11pm. So, maybe I should introduce myself, my name is Liv and I am a second year PhD student in philosophy. My research area is time travel and more specifically the relationship between time travel and free will. I also have a particular interest in philosophy and pop culture. Hence, for this short blog post I am going to explaining how the time travel works (from a philosophical perspective) in a specific film. That film being Harry Potter and the Prisoner of Azkaban.

Time travel?

Well, you may currently be thinking what does studying the philosophy of time travel actually entail, or even is it actually possible to study time travel? Apparently yes, it is possible to study time travel in philosophy and regarding what it entails I mainly look at whether the possibility of time travel necessarily entails any contradictions. If it were to entail contradictions/paradoxes this would seemingly make time travel logically impossible (something we definitely do not want).

We can now take this even further, it is now widely agreed that time travel is logically possible, and so I specifically look at whether this logical possibility causes any issues for intuitions surrounding free will! If free will turned out to be true, I don’t really want time travellers to miss out, you know. Before I get to explaining why the third Harry Potter film is the best time travel film ever there are some crucial assumptions we have to take into account in order to maintain the logical consistency of time travel:

  1. Time travel is not physically possible. We are talking more about pure logical possibility, that is whether time travel entails contradictions. So I am making no claims about whether time travel is physically possible (sorry!)
  2. You cannot change the past! Yup, this is a big one (again sorry!). In order to maintain a nice consistent time travel story, events only happen once and hence if something happened, i.e. if I went back in time and waved at my younger self, it would have always been the case that I waved at my younger self, and so always the case that this event happened. We do not change anything, we simply do what has already happened.

Now let’s get to explaining a very good depiction of logically consistent time travel in film.

Time Travel and Harry Potter

A popular example which shows logically consistent time travel pretty perfectly and concisely is the third Harry Potter. In the first timeline of events we see ‘early’ Harry, Ron and Hermione in Hagrid’s hut discussing the imminent death of their beloved Buckbeak. Suddenly a rock is thrown through the window and breaks a jug, followed by another one which hits Harry on the back. They subsequently notice the Minister arriving at Hagrid’s hut and hasten to leave. We think nothing of these mysterious stones until ‘later’ Harry and Hermione go back in time to save Buckbeak. Harry and Hermione notice their earlier selves are not leaving and so they throw the two stones which notify the students of the Minister.

A picture from the promotional posters of Harry Potter and the Prisoner of Azkaban.

As you can see, ‘later’ Harry and Hermione did not change the past by throwing the stones because their stone throwing had always happened. Events only happen once, the throwing of the stones was just another singular event caused by ‘later’ Harry and Hermione. Consequently Harry and Hermione journey to the past is not inconsistent, and it does not change what has already happened. Nor does not it seem that ‘later’ Harry and

Hermione were fated to throw the stones. Hermione did not think that she had to throw the stones in order to maintain a consistent timeline. She just did throw the stones, she chose to throw the stones.

The third Harry Potter film presents such a simple and concise time travel story, and yet still maintains an interesting story without changing the past! It just goes to show, you don’t need to use time travel to change the past to make it exciting.


There is so much more I can say about the third Harry Potter film and time travel. However, I hope that I have shown a small snippet of what studying time travel entails, and how you can tell an exciting time travel story without changing the past!