Questions: Non-Reductive Physicalism

Question 1

Two creatures are physically identical in every respect. A non-reductive physicalist would predict which of the following?

• A. They may differ in mental properties, since mental properties are not reducible to physical ones and thus not fully determined by them
• B. They are mentally identical — supervenience guarantees no mental difference without a physical difference, even though mental properties do not reduce to physical ones
• C. We cannot determine their mental similarity without first identifying which physical properties each mental property type reduces to
• D. They are mentally identical only if they belong to the same biological species, since multiple realizability is species-relative

Answer: (B)

Non-reductive physicalism maintains supervenience: there can be no mental difference without a physical difference. If two beings are physically identical, they are mentally identical — supervenience is preserved. What the non-reductive physicalist DENIES is reduction: the claim that each mental property type is identical to a specific physical property type. Option A makes the error of thinking that without reduction, supervenience fails — but these are independent claims. You can have dependence without identity.

Question 2

Jaegwon Kim's 'causal exclusion' problem challenges non-reductive physicalism by arguing that:

• A. Mental properties cause too many physical effects simultaneously, violating the causal closure of physics
• B. If every physical effect has a sufficient physical cause and the physical domain is causally closed, mental-level causes appear redundant — there is no causal work left for irreducible mental properties to do
• C. Causal exclusion shows that non-reductive physicalism is indistinguishable from substance dualism in its practical implications
• D. Mental properties cannot supervene on physical properties without reducing to them, making 'non-reductive' physicalism incoherent

Answer: (B)

Causal exclusion works like this: if the physical is causally closed (every physical effect has a sufficient physical cause), and mental events are not identical to physical events, then the mental cause is superfluous — the physical cause already accounts for the physical effect. Mental causation seems to be 'crowded out.' This is the central challenge: non-reductive physicalism wants mental properties to be real causes, but causal closure leaves no room. Non-reductive physicalists have proposed various responses, including arguing that mental and physical descriptions pick out the same causal process.

Question 3

Non-reductive physicalism holds that mental properties are identical to physical properties at a lower level of description.

• T. True
• F. False

Answer: False

This is exactly what non-reductive physicalism DENIES. Reduction would require each mental property type (being in pain) to be identical to a specific physical property type (C-fiber firing). Multiple realizability refutes this identity: pain is realized by different physical states in different creatures, so no single physical property type can be identical to pain. Non-reductive physicalism maintains that mental properties are real and distinct — they supervene on but are not identical to physical properties.

Question 4

Multiple realizability is one of the key arguments supporting non-reductive physicalism, because it shows that the same mental property can be instantiated by very different physical substrates.

• T. True
• F. False

Answer: True

Multiple realizability is the main argument against type-identity theory and for non-reductive physicalism. If pain = C-fiber firing (type identity), then octopuses and robots couldn't feel pain, since they lack C-fibers. But if they can feel pain (same mental property type, different physical realizations), then the identity claim is too strong. Non-reductive physicalism accommodates this: pain is a real mental property that can be multiply realized, not reducible to any one physical property type.

Question 5

Explain the difference between supervenience and reduction, and why a non-reductive physicalist insists that mental properties can supervene on physical ones without being identical to them.

Model answer: Supervenience is a dependence claim: no mental difference without a physical difference. If two beings are physically identical, they are mentally identical. Reduction is an identity claim: each mental property type IS a specific physical property type. Non-reductive physicalism accepts supervenience (the mental depends on and is grounded in the physical) while rejecting reduction (mental properties are not identical to physical ones). The argument is multiple realizability: pain is realized by C-fibers in humans, different neurons in octopuses, perhaps silicon in robots — so pain cannot be identical to any single physical property type, even though every instance of pain is physically realized.

The key philosophical point is that dependence does not imply identity. Water supervenes on H₂O in the sense that water differences require molecular differences — but 'water' and 'H₂O' aren't the same concept. Non-reductive physicalists argue that mental properties are similarly real at their own level: psychological explanation is not just shorthand for neuroscience, and mental properties have their own causal profiles that can't be captured by lower-level physical descriptions.