A philosopher argues: 'Since mental properties supervene on physical properties, mental facts just are physical facts — psychology reduces to physics.' What is wrong with this inference?
ANothing — supervenience entails reduction by definition
BSupervenience establishes dependence and covariation, but not identity or reduction
CThe argument is correct only for strong supervenience, not weak supervenience
DSupervenience applies to properties, not facts, so the inference is a category error
Supervenience captures a one-way determination relation: no A-difference without a B-difference. But this falls far short of reduction, which would require A-properties to be identical to or definable in terms of B-properties. The classic example is aesthetic properties supervening on physical ones — any molecular duplicate of the Mona Lisa would be equally beautiful — without 'beautiful' meaning the same thing as any physical description. Supervenience allows non-reductive physicalism: mental properties depend on physical ones without being reducible to them.
Question 2 Multiple Choice
In two different possible worlds, two beings share exactly the same physical properties but differ in their mental states. Which type of supervenience does this violate?
ANeither — supervenience only applies within a single world
BWeak supervenience only
CStrong supervenience only
DBoth weak and strong supervenience
Weak supervenience only requires that within a single possible world, beings with identical B-properties have identical A-properties. It says nothing about what happens across worlds. Strong supervenience is cross-world: if an object has A-property P in virtue of its B-properties, then any object in any possible world with those B-properties also has P. The scenario described — same physical properties, different mental states in different worlds — violates strong but not necessarily weak supervenience.
Question 3 True / False
If mental properties supervene on physical properties, then two beings with all the same physical properties must have all the same mental properties.
TTrue
FFalse
Answer: True
This is the direct consequence of the supervenience definition: no A-difference without a B-difference. Equivalently (by contrapositive), if two things differ in their A-properties (mental properties), they must differ in their B-properties (physical properties). So fixing all physical facts fixes all mental facts — you cannot have a mental difference while physical properties remain identical.
Question 4 True / False
If A supervenes on B, then A-properties are causally produced by B-properties.
TTrue
FFalse
Answer: False
Supervenience is a logical/modal relation — a pattern of covariation — not a causal claim. Saying mental properties supervene on physical ones does not say physical events cause mental events (though they may); it says only that the distribution of mental properties is constrained by the distribution of physical properties. Supervenience is compatible with many different metaphysical stories about the relationship (grounding, causation, realization, emergence), but it does not itself assert any of them.
Question 5 Short Answer
Why does supervenience allow dependence without reduction, and why is this distinction philosophically important?
Think about your answer, then reveal below.
Model answer: Supervenience says only that there can be no A-difference without a B-difference — fixing the B-level fixes the A-level. Reduction would further require that A-properties are identical to, or fully definable in terms of, B-properties. These are different claims: supervenience is a constraint on covariation, while reduction is a claim about identity or definability. The distinction is important because it makes non-reductive positions coherent: one can hold that moral or mental properties are fully dependent on physical properties without claiming that moral or mental descriptions are translatable into physical descriptions.
This is why supervenience became central to non-reductive physicalism. Philosophers wanted to avoid substance dualism (which says minds exist separately from bodies) without committing to eliminativism (which says there are no mental facts, only physical ones). Supervenience offers a middle path: mental facts are real but not fundamental — they are fully grounded in physical facts without being identical to them.