Supervenience (from Latin supervenire, to come upon, to supervene) — A relation between two sets or families of properties according to which there can be no difference in the supervenient set without a difference in the base set. Formally: properties B supervene on properties A if and only if any two objects (or events, states, etc.) that are indistinguishable in all A-properties are necessarily indistinguishable in all B-properties. Supervenience expresses a relation of dependence and co-variation without requiring reduction: the supervenient set depends on the base, but cannot be defined or eliminated in favour of it.

Origins: Ethics and Philosophy of Mind

The term acquired technical philosophical rigour in two independent contexts that converge in the twentieth century.

In ethics, R.M. Hare used the concept in The Language of Morals (1952) to capture a fundamental intuition: moral properties depend on natural properties. If two objects or actions are identical in all their descriptive natural properties (size, shape, consequences, etc.), they must have the same moral value. Hare does not yet use the term “supervenience”, but the relation he describes is precisely this one.

In the philosophy of mind, Donald Davidson was the first to use the term technically in “Mental Events” (1970, in Experience and Theory, ed. Foster and Swanson). Davidson argues that mental events are identical to physical events, but that mental predicates are not reducible to physical predicates — a position known as anomalous monism. In this context, he writes that mental properties supervene on physical ones: there can be no mental difference without a physical difference, but mental predicates are not definable in physical terms.

Types of Supervenience

Jaegwon Kim, who systematised the concept from the 1980s onwards (see Supervenience and Mind, 1993), distinguishes at least three forms:

  • Weak supervenience: for every pair of objects in the same possible world, indistinguishability in A implies indistinguishability in B.
  • Strong supervenience: across all possible worlds, indistinguishability in A implies indistinguishability in B.
  • Global supervenience: considers indistinguishability between entire possible worlds, not just between individual objects.

The differences have important metaphysical consequences: strong supervenience is compatible with metaphysical necessity; weak supervenience, only with local co-variation.

Problems and Debates

Kim argued influentially that supervenience, by itself, does not resolve the mind-body problem: it is compatible with both dualism and physicalism. Moreover, Kim proposed the “causal exclusion argument”: if mental events supervene on physical events, and physical events have sufficient physical causes, it seems that mental events are causally idle — which would be problematic for Davidson’s anomalous monism and for any non-reductive physicalism.

In ethics, moral supervenience has been extensively debated: is it a logical, metaphysical, or merely contingent necessity? Its acceptance is compatible with moral non-naturalism (the position of Hare and G.E. Moore, Principia Ethica, 1903) or does it require naturalism?

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