There is an extension of that idea, which is to suppose that we could make a silicon neuron that can perfectly replace an organic one (state and all). Then you

There is an extension of that idea, which is to suppose that we could make a silicon neuron that can perfectly replace an organic one (state and all). Then you can replace neurons in the brain one by one, and the brain carries on functioning exactly like it always has. Eventually the brain is entirely silicon, but to the owner subjectively nothing has changed, they are as 'conscious' as they ever were.