Compare dualist and physicalist theories of mind and evaluate the hard problem of consciousness

What this dot point is asking

You need to set out dualism and the leading physicalist theories, explain the hard problem, and weigh the strengths and objections of each.

Substance dualism

René Descartes argued that the mind is a non-physical thinking substance distinct from the extended, physical body. His main argument is one of conceivability: he can clearly conceive of his mind existing without his body, so they must be distinct. Dualism captures the intuition that thoughts and sensations seem utterly unlike grey matter.

The decisive objection is the interaction problem, pressed by Princess Elisabeth of Bohemia. If the mind is non-physical and unextended, how can it cause the body to move, and how can the body cause sensations in the mind? Causal interaction between radically different substances seems mysterious, and it appears to violate the conservation of energy in the physical world.

Physicalist theories

Physicalism holds that everything, including the mind, is ultimately physical. Three versions matter.

Logical behaviourism, associated with Gilbert Ryle, identifies mental states with dispositions to behave. To be in pain just is to be disposed to wince and complain. Ryle ridiculed dualism as the dogma of the ghost in the machine. The objection is that it ignores the inner felt quality of experience and seems to leave out what pain actually feels like.

The mind-brain identity theory, defended by J. J. C. Smart and U. T. Place, says mental states simply are brain states, just as lightning turned out to be an electrical discharge. It is clean and scientific, but faces the multiple realisability objection: creatures with very different brains, or even a silicon machine, could plausibly share a mental state such as pain, so pain cannot be identical to one specific brain state.

Functionalism, developed by Hilary Putnam, answers this by identifying mental states with their causal-functional role, what they do, rather than their physical make-up. Pain is whatever state is caused by damage and causes avoidance behaviour, regardless of the stuff that realises it. Functionalism dominates modern philosophy of mind, but critics argue it too leaves out subjective feel, as Ned Block's absent-qualia thought experiments suggest.

The hard problem of consciousness

David Chalmers distinguishes the easy problems of explaining cognitive functions from the hard problem: why is any of this accompanied by subjective experience, or qualia? Thomas Nagel posed the issue by asking what it is like to be a bat, arguing that the bat's point of view escapes any purely physical description. Frank Jackson's knowledge argument imagines Mary, a scientist who knows every physical fact about colour vision but has only seen black and white. When she first sees red she seems to learn something new, what red looks like, suggesting that physical facts do not exhaust the facts about experience.

These arguments do not prove dualism, and physicalists reply in various ways, for instance that Mary gains a new ability rather than new propositional knowledge. But they sharpen a genuine explanatory gap that no theory has closed to general satisfaction.

Evaluating

A strong answer recognises a trade-off. Dualism honours the distinctiveness of consciousness but cannot explain mind-body interaction. Physicalist theories fit science and explain behaviour and function, yet each is dogged by the worry that it leaves out subjective experience. The hard problem is the sharpest form of that worry. The most defensible stance is probably a cautious physicalism that takes the explanatory gap seriously rather than dismissing it.