The mind-body problem and theories of mind: QCE Philosophy and Reason
“Explain and evaluate theories of mind, including substance dualism, physicalism and functionalism, and the problem of consciousness”
The mind-body problem asks what the mind is and how it relates to the body. Descartes's substance dualism holds mind and body are distinct substances, thinking versus extended, but faces the interaction problem of how the non-physical could cause physical change. Physicalism holds everything is physical; the identity theory says mental states are brain states, but multiple realisability objects that the same mental state could be realised in different physical systems. Functionalism defines mental states by their causal role rather than their make-up, accommodating multiple realisability but seeming to omit subjective feel. The hard problem of consciousness asks why there is any subjective experience (qualia) at all, dramatised by Jackson's knowledge argument about Mary the colour scientist.
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What this dot point is asking
QCAA wants you to engage a core question of metaphysics: what is the mind, and how does it relate to the physical body? You need the main theories (substance dualism, physicalism including identity theory, and functionalism), their key arguments and objections, and the hard problem of consciousness. This connects to free will and personal identity.
The answer
The problem
We seem to be both physical bodies and conscious minds. Mental states (thoughts, pains, experiences) feel utterly unlike physical states (neurons firing), yet they interact: a pin causes pain, a decision moves an arm. The mind-body problem asks what minds are and how the mental and the physical relate.
Substance dualism
Rene Descartes, in the Meditations (1641), defended substance dualism: mind and body are two distinct kinds of substance. The body is extended matter, governed by physics; the mind is an unextended, thinking, non-physical thing. His argument: I can doubt that my body exists but cannot doubt that I think, so mind and body have different essential properties and must be distinct. Strength: it respects the obvious difference between thought and matter and leaves room for an immaterial soul. The decisive objection is the interaction problem (pressed by Princess Elisabeth of Bohemia): how can a non-physical mind cause physical events in the brain without violating the conservation of energy? Causal interaction between radically different substances is deeply obscure.
Physicalism and identity theory
Physicalism (materialism) holds that everything, including the mind, is physical. The mind-brain identity theory says mental states just are brain states (pain is the firing of certain neurons), as water is H2O. Strength: it fits the scientific picture and dissolves the interaction problem, since there is only one kind of stuff. Objection from multiple realisability (Hilary Putnam): the same mental state (pain) could be realised in very different physical systems (humans, octopuses, perhaps machines), so a mental state cannot be identical to one specific brain state.
Functionalism
Functionalism responds: a mental state is defined not by its physical make-up but by its functional role, its causal relations to inputs, outputs and other mental states. Pain is whatever state is typically caused by injury and typically causes wincing and avoidance, whatever realises it. This accommodates multiple realisability and underpins the idea that minds could be implemented in different hardware. Objection: functional role seems to leave out what it feels like, the subjective quality of experience.
The hard problem of consciousness
David Chalmers distinguishes the "easy" problems (explaining functions such as perception and attention) from the hard problem: why is there subjective experience at all, the felt quality of seeing red or tasting coffee (qualia)? Frank Jackson's knowledge argument dramatises this: Mary, a brilliant scientist who knows every physical fact about colour vision but has lived in a black-and-white room, seems to learn something new when she first sees red, namely what it is like. If so, there are facts about experience beyond the physical facts, which challenges physicalism. Replies include denying Mary learns a new fact (she gains an ability or a new mode of acquaintance, not new information).
Lay out Jackson's argument formally, then test a response.
Step 1: State the premises about Mary
P1: Before release, Mary knows all the physical facts about colour vision. P2: On first seeing red, Mary learns something new (what it is like to see red).
Step 2: Draw the anti-physicalist conclusion
If Mary already knew all the physical facts (P1) yet learns something new (P2), then what she learns is a non-physical fact. C: So not all facts are physical, and physicalism is false.
Step 3: Identify the premise the physicalist targets
The physicalist accepts P1 but reinterprets P2. The ability reply says Mary gains a know-how (the ability to imagine, recognise and remember red), not a new propositional fact. The acquaintance reply says she gains a new way of being acquainted with a fact she already knew.
Step 4: Evaluate the dispute
If P2 is read as gaining an ability or mode of acquaintance, the argument no longer shows a new fact about the world, so physicalism survives. The force of the argument then depends on whether "what it is like" is genuinely new information or merely a new grasp of old information, which remains contested.
If mind and body are utterly different substances, it is obscure how a non-physical mind could cause physical changes in the brain without breaching the conservation of energy. This objection, pressed by Princess Elisabeth, is the main reason most modern philosophers reject Cartesian substance dualism in favour of some form of physicalism.
- Confusing dualism with religion
- Substance dualism is a metaphysical thesis about kinds of substance, argued on rational grounds, not merely a doctrine of faith.
- Treating identity theory and functionalism as the same
- Identity theory ties a mental state to a specific brain state; functionalism ties it to a causal role that many physical states could fill.
- Ignoring multiple realisability
- It is the key objection to the identity theory and the main motivation for functionalism.
- Missing the hard problem
- Explaining cognitive functions does not obviously explain why there is subjective experience at all.
Try this
Q1. Explain Descartes's argument for substance dualism and the interaction objection. [4 marks]
- Cue. Mind and body have different essential properties (thinking versus extension); the objection asks how a non-physical mind causes physical change.
Q2. Explain multiple realisability and what it objects to. [3 marks]
- Cue. The same mental state can be realised in different physical systems, so a mental state is not identical to one brain state.
Q3. Outline Jackson's knowledge argument. [3 marks]
- Cue. Mary knows all physical facts about colour but learns something new on first seeing red, suggesting non-physical facts about experience.
Exam-style questions
Questions in the style of QCAA exam questions on this dot point, each with a worked answer. They are written by ExamExplained unless tagged "Past paper"; the year shows the paper a question is modelled on.
Practice7 marksEvaluate substance dualism as a theory of mind, with reference to at least one objection and one rival theory.Show worked answer →
A 7 mark response explains dualism, an objection, and a physicalist rival.
Substance dualism. Descartes holds mind and body are distinct substances: the body is extended matter, the mind an unextended thinking thing. His argument: I can doubt my body exists but not that I think, so they have different essential properties and must be distinct.
Strength. It respects the apparent gulf between thought and matter and leaves room for an immaterial self.
Objection (interaction problem). If the mind is non-physical, it is obscure how it could cause physical events in the brain without breaching the conservation of energy, as Princess Elisabeth pressed. Causal commerce between radically different substances is unexplained.
Rival. Physicalism (identity theory) holds mental states just are brain states, dissolving the interaction problem by positing one kind of stuff, though it faces multiple realisability.
Verdict. The interaction problem makes substance dualism hard to sustain, so most philosophers prefer a physicalist or functionalist account, despite the unresolved hard problem of consciousness.
Markers reward an accurate account of dualism, the interaction objection, a stated rival, and a justified conclusion.
Practice5 marksExplain Jackson's knowledge argument (the case of Mary) and assess whether it refutes physicalism.Show worked answer →
A 5 mark response presents the argument and evaluates it.
The argument. Mary knows every physical fact about colour vision but has lived in a black-and-white room. On first seeing red she seems to learn something new, namely what it is like to see red (a quale). If she learns a new fact despite already knowing all the physical facts, then there are non-physical facts about experience, so physicalism is false.
Assessment. The argument is powerful because it isolates subjective quality (the hard problem). But physicalists reply that Mary gains a new ability or a new mode of acquaintance with a fact she already knew, not a new fact (the ability and acquaintance replies). If those replies succeed, the argument shows a gap in our concepts, not in the world.
Verdict. The knowledge argument poses a serious challenge to physicalism but is not decisive, since the ability/acquaintance replies offer a physicalist reading.
Markers reward an accurate statement of the Mary case and a critical assessment using at least one physicalist reply.