Mind and body · Quiz question 9/35
Gradual Neural Replacement (Fading Qualia)
Replace your neurons one by one with chips that work exactly the same. Does your consciousness survive? David Chalmers's fading qualia argument and John Searle's reply.
Your neurons are swapped out one by one for silicon chips that work exactly the same. After a year your brain is all chips — and you talk and act exactly as before.
Your consciousness stays intact the whole way through.
Gradually swapping neurons for functionally identical parts was discussed by Zenon Pylyshyn (1980) and others, but the most cited version is David Chalmers's 1995 paper "Absent Qualia, Fading Qualia, Dancing Qualia." Chalmers argued that if consciousness faded during the swap, you'd end up in a bizarre state — experiences dimming while you keep saying "nothing's changed" — so it's more reasonable to think the same functional organization means the same consciousness. John Searle (1992) held that in the same scenario, behavior could stay the same while consciousness vanished.
This question asks what consciousness depends on: the material (carbon-based neurons) or the functional organization (how information flows)? If you agreed, you're close to functionalism: build the same organization in silicon and you get the same mind. That also bears directly on whether AI could be conscious.
Interestingly, Chalmers's argument supports a functionalist conclusion even though he leans dualist. He thinks consciousness may not reduce to physics but is lawfully tied to functional organization. Searle thought consciousness comes from the brain's specific biological causal powers — so the swap could end with you still saying "I'm fine" while things go dark inside.
Consciousness depends on functional organization, not material. Same organization, same experience.
Key names: David Chalmers (organizational invariance), Daniel Dennett, early Hilary PutnamConsciousness comes from the brain's biological causal powers. Mimicking function might lose it.
Key names: John SearleConsciousness just is certain neural states — the question is whether the chips really play the same physical role.
Key names: Paul Churchland, J. J. C. SmartIn the 2020 PhilPapers Survey, functionalism was the most popular theory of consciousness, chosen by about 33% of philosophers.