china brain

Functionalism holds that anything that can perform the same functions as a brain is able to have mental states as humans do. There is one common objection to this theory that makes this statement seem almost ridiculous.

There are about 10 billion neurons (brain cells) in the adult human brain. There are over a billion people in China, but lets just suppose that there are 10 billion people there (The original thought experiment uses China, so I'll stick with it). Imagine that each person is given a set of strings connecting them to a number of other people, who each have their own set of strings connecting them to others. Each person is then given the same duty as a respective neuron in the human brain. The whole nation, the "china brain", is now able to carry out every function a brain could potentially carry out. Would this china brain achieve mental states, and thus consciousness?

According to a functionalist, the answer should be yes. But how can that be? A functionalist could very well argue that the china brain would think no differently than a human, but it seems to go against all common sense that this be the case. It seems, looking at this example, that an actual human brain is necessary to achieve mental states. This is a belief of the type identity theory of the mind, discussed below. So in light of this objection, type identity theory actually seems more plausible.