physicalist theories of mind including identity theory and functionalism, and their objections

What this dot point is asking

VCAA wants you to explain the main physicalist theories of mind, identity theory, behaviourism and functionalism, and to assess whether any of them can fully account for mental states. The high-band response distinguishes the theories precisely (they are not the same physicalism), matches each objection to the theory it targets, and reaches a judgement about whether the explanatory gap defeats physicalism or merely embarrasses it.

The physicalist theories

Logical behaviourism

Gilbert Ryle, in The Concept of Mind, attacks Descartes as committing a category mistake, treating the mind as a ghost in the machine, a thing of the wrong logical type. On Ryle's behaviourism, mental terms refer not to inner private events but to dispositions to behave. To be in pain is to be disposed to wince, groan and avoid the cause. The objection is decisive enough that few hold it today: it cannot account for the felt quality of pain, and it seems to leave out the inner episode entirely (a perfect actor could fake every disposition).

Type identity theory

J. J. C. Smart and U. T. Place defend the identity theory: mental states are identical to brain states, just as lightning is identical to electrical discharge. Pain is the firing of C-fibres. This is a type identity: every instance of the type pain is an instance of the type C-fibre firing. The theory is ontologically economical and fits neuroscience, but it makes a strong empirical bet.

Functionalism

Hilary Putnam argues that what makes a state a mental state is its causal role, its pattern of inputs, outputs and relations to other states, not its physical realisation. Pain is whatever state is caused by tissue damage and causes wincing and the desire for it to stop. Functionalism is the dominant physicalist-friendly view because it allows the same mental state to be realised in different substrates.

The objections

Multiple realisability (against identity theory)

Putnam's central objection to type identity: pain can plausibly occur in humans, octopuses and (conceivably) silicon-based aliens whose brains share no physical type with ours. If pain were identical to C-fibre firing, only creatures with C-fibres could feel pain. Since that is implausible, mental types cannot be identical to physical types. Functionalism survives this objection because it defines states by role, not material.

Qualia and the knowledge argument

Frank Jackson's Mary the colour scientist knows every physical fact about colour vision while confined to a black-and-white room. On release she learns something new, what red looks like. If she learns a new fact, then not all facts are physical facts, and physicalism is incomplete. The target is any physicalism that claims to capture the felt quality (qualia) of experience. Thomas Nagel makes the same point asking what it is like to be a bat: the subjective character of experience seems to escape objective physical description.

The Chinese Room (against functionalism as a theory of understanding)

John Searle imagines a person in a room manipulating Chinese symbols by rule-book, producing fluent replies without understanding a word. The room has the right functional organisation yet lacks genuine understanding (intentionality). Searle concludes that running the right program (the right functional profile) is not sufficient for a mind. The target is strong functionalism and the computational theory of mind.

Evaluation

Physicalism's great strength is parsimony and its fit with science: it posits no extra substances and explains mental causation without the interaction problem that sinks substance dualism. Functionalism in particular elegantly handles multiple realisability and underwrites artificial intelligence research.

The serious cost is the explanatory gap (Joseph Levine): even granting that pain is C-fibre firing or a functional state, it remains an open question why that state feels the way it does. The Mary and bat arguments dramatise this. A functionalist can reply that Mary gains a new ability or a new mode of presentation of an old fact, not a new fact (the ability hypothesis), which blunts but does not close the gap. Searle's Chinese Room can be met by the systems reply: the person does not understand, but the whole system does. Both replies are live, neither is conclusive.

Judgement: physicalism, and functionalism as its best version, is the strongest available theory of mind because it avoids dualism's causal mystery and accommodates multiple realisability. But it has not closed the explanatory gap, so a complete account of consciousness remains unfinished. The honest verdict is that physicalism wins on cost-benefit grounds while conceding that qualia are its hardest unsolved problem.