The Gradual Brain-Swap Problem

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The Gradual Brain-Swap Problem

Imagine that instead of swapping one whole brain for another in a single surgical act, we did it slowly, remapping A’s cortical organisation bit by bit until it matched B’s. Perhaps I am to be remapped to my wife (and conversely of course).

At the start, nothing noticeable would happen. A single altered neuron would mean nothing to experience. But as more local circuits were replaced, consciousness would begin quietly rewriting itself from within. Not with a dramatic fracture, but with drift.

Consciousness is not a little spectator lodged in the head, peering at mental content. It is the brain’s ongoing activity of holding a world, selecting, associating, weighting and modelling. The brain does not so much have a self as continually produce one.

As my neural pattern was progressively transformed, my self would not suddenly vanish; rather, the very process that generates consciousness would begin generating a somewhat different subjectivity. Saliences would shift. Emotional tone would tilt. Some memories would lose their grip while alien associations began to feel oddly natural. My inner world would not go dark; it would be revised in place.

From the inside, that would probably feel less like death than like mounting strangeness: a sense that the self I had always taken for granted was becoming less familiar, though without any clean moment at which I could say: that was where I ended. The system would still be producing a first-person world, but an increasingly different one, threaded through with memories that no longer felt quite mine. 

The river would keep flowing, but by degrees it would become another river. I'm not sure this would be any consolation to my wife - whom I had now become.

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