Property Dualism

Property dualism is the position in Philosophy of Mind that, while there is only one kind of substance in the universe (physical substance), mental phenomena have properties that are irreducibly distinct from — and not fully explicable by — physical properties. The mind is not a separate substance from the body, but it has phenomenal properties — the felt qualities of experience, or qualia — that no physical description captures.

Property dualism is the philosophical home of David Chalmers's Hard Problem of Consciousness: the problem of explaining why any physical process gives rise to subjective experience at all. On the property dualist view, this problem is genuine and in principle unsolvable by physical science, because physical science describes structure and function while experience is not exhausted by structure and function.

The position faces pressure from both directions. From physicalists: if phenomenal properties make no causal difference (epiphenomenalism), they are explanatorily idle and their postulation violates parsimony. If they do make a causal difference, they must enter the physical causal order — at which point they look like physical properties, and the distinction collapses. From panpsychists: if phenomenal properties are fundamental, why restrict them to organized biological systems? Their presence in organized neurons seems arbitrary without an account of what organizational threshold triggers phenomenology.

Property dualism's relationship to functional state theory is contentious: property dualists hold that functional organization is insufficient for consciousness — that phenomenal properties are something over and above functional organization — while functionalists deny this. This is the live fault line in contemporary Philosophy of Mind.