(In Ned Block’s thought experiment, each member of the Chinese population performs the same functions as a neuron in the brain. he population of China is 1.4×109 people, while a human brain is estimated to have ≈1011 neurons. )
The China brain thought experiment involves imagining what would happen if every member of a great nation, in this case the Chinese nation, were asked to simulate a brain process elementary by communicating with the other members and by following precise instructions by radio links. The question raised by this fiction is related to an objection to the functionalist conception of the mind, which identifies mental states not with determinate neurophysiological states, but with functions or “causal roles” that can be fulfilled by different types of states. The question in this context is whether a complex combination of different tasks carried out by human agents (themselves endowed with minds) could produce a mind or a consciousness in the same way as the brains of these agents. China brain has all the elements of a functional description of the mind: sensory inputs, behavioral outputs, and internal states causally related to other internal states. If this system could be made to act the way the brain of a conscious being does, then, according to functionalism, it would itself have a consciousness, which seems counter-intuitive.
The first versions of this scenario were proposed in 1961 by the Soviet physicist Anatoly Dneprov, in 1974 by Lawrence Davis, then in 1978 by the philosopher of the mind Ned Block, who was the first to consider the case where each member of the Chinese population would fulfill the same functions as those of a neuron in the brain. Block argues that China-brain thus understood would have no mind in the sense we commonly understand it. Unlike Block, proponents of functionalism believe there is no reason to rule out the idea that China-brain has a mind. Relying on the principle of multiple realizability of mental states – the same mental state such as fear being able to be realized in different ways in very different animal species – they consider that neurons are not, at least in principle, the only material who can achieve a mental state. For Daniel Dennett, in particular, the fact of attributing a spirit in a justified way to a system (biological or artificial) does not come from ontological considerations on what a spirit really is, but from an interpretative strategy to predict behavior of the system, and there is therefore no reason to consider functionally equivalent behavior differently.
China brain is a fiction imagined above all to show the problematic nature of consciousness when it is conceived within the framework of functionalism. In this sense, he is one of the figures of what is now called the “absent qualia argument”, and is comparable in this to the philosophical figure of the “zombie” put forward by David Chalmers. Like the latter, Ned Block claims to show that it is possible for something to be functionally equivalent to a conscious being without necessarily being a conscious being itself, and therefore that a functional system alone cannot produce a mind capable of thoughts and feelings. This line of argument against functionalism, often likened by its detractors to “a pump of intuition”, has itself many objections. David Cole, for example, remarks that we can reverse Block’s thought experiment by imagining that each of our neurons is itself fully aware of the electro-chemical activity that it carries out and undergoes. There is every reason to suppose that our neurons would then find it implausible that their collective activity could produce consciousness or intentionality.
(Includes texts from Wikipedia translated and adapted by Nicolae Sfetcu)