In my first ever blogpost I speculated whether uploading your brain would result in potentially eternal life. And I concluded it was possible. However, I also concluded that what we experience as our self is not as continuous as we believe. I kind of glossed over the reasons I believe that to be true. Since elaborating this allows me to talk about two of my favourite thought experiments, I decided to write this short add-on.
The malicious demon thought experiment by Descartes supposes there is a being that can produce a complete illusion of the external world:
I shall think that the sky, the air, the earth, colours, shapes, sounds and all external things are merely the delusions of dreams which he has devised to ensnare my judgement. I shall consider myself as not having hands or eyes, or flesh, or blood or senses, but as falsely believing that I have all these things.
This idea of course has been used many times. It is the plot of the movie Matrix and is also used for the simulated reality or the brain in a vat arguments. It is perfect to demonstrate that we are unable to tell apart reality and illusion, if the illusion is good enough.
The “five minute hypothesis” by Bertrand Russel works in a similar way, but goes even further. It assumes that everything in the universe, including human memory, sprung into existence five minutes ago. In this scenario an event that you remember does not necessarily have to have happened, as long as the molecular structures of the memory were put in place also five minutes ago and, thereby, create the illusion that it happened. It is impossible to prove that this hypothesis is wrong. Of course, it is also not possible to prove that it is correct and entertaining it as a real possibility is mostly meaningless. Rather, you may use it to scrutinize your feeling of continuity of self. To this end, if neuroscience were able to prove that a continuity of the self exists outside of plastic brain changes (i.e., the molecular structures of the memory), it would disprove this hypothesis.
So far I am unaware of such data and I believe it is highly unlikely they will ever exist.