This week I watched the premiere of Rick and Morty season 4. Something in the episode brought me back to thought experiments concerning the issue of determinism. Before continuing, those who are fans of the show and have not seen this episode read no further since it will contain spoilers.
In the episode, Morty discovers a crystal that allows him to view his own death. However, every decision he makes changes the future death he will experience, thus the crystal showing Morty a new death. The crystal also shows multiple possible future deaths that become the predicted death if Morty makes certain decisions. Morty notices a possible future death of dying as an old man with Jessica: a girl he is infatuated with at his school. Morty throughout the episode uses the crystal so he can make every decision that will bring about that specific death, since it assumes that he ended up with Jessica.
At the end of the episode, Morty discovers that the future he was viewing was him in a nursing home on his deathbed and Jessica was merely a nurse comforting him, hence was following a path that would never result in them being together.
Rick and Morty is a show well known for its combination of deep philosophy with extreme silliness, and this episode is no exception. The first philosophical point this plot makes is about epistemology about determinism. Determinism is the view that all of our thoughts and actions are fully caused by prior events, which raises questions about whether we have free will. Ignoring the free will problem, many will argue that it will be impossible to know whether determinism is true. This is known as the problem of foreknowledge.
A thought experiment about the problem of foreknowledge was put forward by wireless philosophy (below is the link to their video for those interested). Imagine a book that tells you the entire story of your life up until your death. You read this book up until it is at the point where it says ‘you are now reading the book of your life’. The book has been 100% accurate so far. You now have the ability to skip pages and view your own future.
In world where determinism is true and such a book exists, the only way this could be possible is that you would have to be unable to contradict what is said on that page. However, it seems that we could easily do so. Say the book said on the next page I had chicken for lunch, I could easily just have salad. If this is possible, the book would be wrong. And if the book is wrong, either foreknowledge is impossible and/or determinism is false.
A possible way around this is another thought experiment I put forward to my students in primary ethics from the ‘Story of Osmo’. In the story, Osmo also had a book of his life, he skips to his death and reads that he will die in a plane crash from O’Hare to Fort Wayne on his 29th birthday. On his 29th birthday, he catches the O’Hare to St Paul instead. However, the plane diverts to Fort Wayne and crashes killing Osmo.
So, in this case the book remains true regardless of any attempt to change the outcome. Even with the foreknowledge. However, say one were to read the book in its entirety so all details are known. In that case, the book would simply be ‘you are reading this page, you are reading this page, you are reading this page’ ad infinitum.
Returning to the plot in the Rick and Morty episode. Unlike the book of your life, the crystal shows multiple possible deaths, with the current one in clear vision. Hence, you are allowed to change outcomes. This raises the question of whether the Rick and Morty universe is assuming a fully deterministic one or an indeterministic one. The premise of the series is that Rick and Morty do live in a multiverse, with an infinite number of alternate versions of Rick and Morty. But the crystal is predicting the death of Morty in his current universe, so the fact that they live in a multiverse is irrelevant.
If the Rick and Morty universe is a fully deterministic one, then the crystal would have to know in advance Morty would find the crystal and all the choices Morty would make. However, that would mean the possible future deaths were never possible, since it was always determined that Morty would avoid those deaths to pursue his ambition to die as an old man with Jessica. Therefore, at least in this episode, the Rick and Morty universe would have to be indeterministic.