Absent / inverted qualia
Explanation
The thought experiments of absent qualia and inverted qualia are classic tools in philosophy of mind for testing functionalist theories. The absent qualia argument asks: could there be a system functionally identical to us but without any conscious experience? It is the case of the philosophical zombie in its localised version.
Ned Block proposed in 1978 his famous Chinese nation: imagine that the entire population of China organises itself to functionally simulate the human brain, each person doing the work of one neuron, communicating by telephone. The resulting system would be functionally equivalent to a brain. Would it feel anything? Common intuition says no, that a nation of people would not have a unified experience of pain or colour. If the intuition is correct, functionalism is false.
The inverted qualia argument moves in another direction. Imagine two functionally identical people: both call red red, both say red is warm, both stop at red traffic lights. But while one sees red internally as we do, the other sees internally what we call green (although she also calls it red through linguistic learning). Would this be possible? If so, qualia are not determined by function.
These thought experiments point in the same direction: qualia —the subjective qualities of experience— seem separable from the functional organisation of the system. If they are separable, functionalism (which identifies mind and function) does not capture the whole of mental reality. There must be something more than function: either specific physical properties (as Searle argues), or fundamental phenomenal properties (as panpsychists argue).
Functionalist responses are equally elaborate. Some deny that the scenarios are really conceivable in a metaphysically relevant sense. Others deny that the intuition is reliable: perhaps a functionally identical Chinese nation would feel something (even if we find it hard to imagine), and perhaps inverted qualia are impossible under sufficiently rich functional constraints.
The debate remains alive and has become more sophisticated. The thought experiments have been criticised (are we really imagining what we think we are?) and refined (which kind of functionalism exactly do they attack?). Today they continue as a litmus test: any theory of consciousness must explain why we have the intuitions of absent and inverted qualia, either to justify them (property dualism, panpsychism) or to dissolve them (eliminativism, sophisticated functionalism).
Strengths
- Memorable and philosophically influential arguments.
- Capture the intuition of the irreducibility of qualia.
- Have pressed functionalism to refine its positions.
- Connect with integrated information theory.
Main critiques
- Reliance on intuitions that may be revisable.
- Functionalists consider them ill-formed or incoherent.
- The inverted quale may be empirically unverifiable.
- Dennett: not really conceivable under scrutiny.