Continuity of self: Was the world put into place five minutes ago?

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.

vision by Kaitlin M is licensed under CC BY 2.0

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.

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Theseus Brain: Can you prolong your life by uploading your brain to a computer?

The idea of living forever in a digitalised form has become popular and recently even featured in the Dr. Who Christmas Special 2017. [SPOILER] An advanced civilisation kidnaps individuals at the very last second of their lives, extracts all their memories and returns them for their deaths. It is revealed that this enables the individual to come back to life using an avatar resembling their body shortly before death. [/SPOILER]

Most people will intuitively answer the title question with a strict ‘no’. Thinking about it for a while the answer may change towards ‘yes, but’. Assume a process will someday be engineered, by which the exact physiological properties of your brain can be emulated within a software running on a powerful computer. This emulation would by definition include all your memories and adapt to experiences in the exact same as your brain would have. Most people will agree that we are far from discovering this technology and in fact the laws of quantum mechanics may even prevent it. For sake of argument in this post, I will assume that it will someday be possible. Will that mean you can live forever?

In a way this idea is not very new, as it entails the classical problem of identity. The most ancient thought experiment in this domain is the Ship of Theseus or the Theseus paradox. The Grandfather’s Axe is a modern version of this conundrum: imagine an axe is passed down in the family over generations and over time both head and handle are replaced. Is it still the same axe? (Of course the axe would claim to be the same axe, if you asked it, but that’s whole other story.)

In a similar way, you can ask what would be the consequence of replacing one single biological neuron in a human’s brain with one single artificial neuron that mimics all of the original neuron’s connections and functions. Would this make the respective human a different individual? Over time, you could exchange one neuron, then another, and another until the whole brain is made up of artificial neurons. At what point is the person no longer the original? Most people would agree that this gradual change, if it takes place over a period of say years, would mean the person stays the same individual, whereas, making an artificial copy of the original brain (which is in all important ways equivalent to uploading it to a machine) would mean the new individual is not the same as the original. (This is essentially a rephrasing of the teleportation paradox.)

This paradoxical differentiation is due to a strong subjective feeling of continuity that is violated by the idea of uploading or copying people’s brains. For example you feel this continuity, when you wake up after a night of sleep and are convinced that you are the same person as when you went to bed (I stole this great example from Guilio Tononi’s Phi). As far as we know, this feeling is merely a product of sampling the memories of being yourself and realizing you have not changed. Put more drastically, the only thing that keeps your experience of self continuous, is the constant plastic changes that are occurring in the brain and producing congruent memories that can be sampled. Unless one argues that there exists something like a non-material soul, all these memories can potentially be part of a brain-upload.

In conclusion, there is no difference between the experience of uploading your brain to a computer and experiencing the flow of time in your dedicated biological body. Not because you remain yourself when you are uploaded, but because there is no continuous self. In this sense continuity of self is an illusion and an upload of all your memory would in essence enable eternal life. However, this absence of actual continuity of existence also means that your life only lasts a moment. In the each new moment a fleeting individual is born that inherits all you memories and only lasts a moment before it again is replaced.

If this sounds a bit depressing, you can console yourself with this: When you are out partying and have that one drink too many, it’s not you who suffers that hang-over but future-you. And who cares about her?

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Is there anybody out there?

So finally I have gotten around to activating this site. It has been sitting around now for about two months and as the dust settles I just wanted to send out a quick hello in case anybody is listening. This page is intended for my personal musings and I hope I can regularly post things about neuroscience, philosophy and current developments. Of course, this page is merely a sly trick to advance my career, so don’t expect any actual original content. That’s it for now, watch out for my first actual post though…

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