What is the multiple-realizability argument?

Fodor argues that a higher-level property such as 'being in pain' or 'being money' can be realized by indefinitely many distinct physical states. Because there is no single physical kind to identify it with, the higher-level generalization cannot be reduced to a law of physics, supporting the autonomy of the special sciences.

Reduction and Emergence

Reduction and emergence concern whether higher-level sciences can be derived from lower-level ones, or whether higher-level phenomena are genuinely novel.

Definition

Reduction is the relation by which one theory or level of description is shown to be derivable from or explained by another, more fundamental one; emergence is the thesis that some higher-level properties are novel and not so derivable, while typically depending on lower-level facts.

Scope

This topic covers Nagel's classic model of intertheoretic reduction via bridge laws, the multiple-realizability argument against reduction in the special sciences, and accounts of emergence and supervenience, including the question of whether emergent properties have distinctive causal powers.

Core questions

Can higher-level theories be reduced to physics via bridge laws?
Does multiple realizability block reduction of the special sciences?
What is the relation between supervenience and emergence?
Can emergent properties exert downward causal influence?

Key concepts

bridge laws
intertheoretic reduction
multiple realizability
supervenience
downward causation
causal exclusion
unity of science

Key theories

Nagelian reduction: Nagel models reduction as the derivation of a reduced theory's laws from the reducing theory plus bridge laws connecting their vocabularies.
Multiple realizability and antireductionism: Fodor argues that special-science kinds can be realized by heterogeneous physical states, so their generalizations cannot be reduced to physics.
Critique of emergence: Kim argues that strong emergence with downward causation faces a causal-exclusion problem given the causal closure of the physical.

History

Nagel's 1961 model of reduction expressed the logical-empiricist ideal of a unified science. Putnam's and Fodor's 1970s multiple-realizability arguments defended the autonomy of the special sciences, while Kim's work on supervenience and the exclusion problem in the 1990s sharpened the challenge to non-reductive physicalism and emergence.

Debates

Reductionism versus the autonomy of the special sciences: Reductionists seek to derive higher-level theories from physics, while Fodor and others argue that multiply realized kinds support genuine, irreducible special-science laws.

Key figures

Ernest Nagel
Jerry Fodor
Jaegwon Kim
Hilary Putnam

Seminal works

nagel1961
fodor1974
kim1999

Frequently asked questions

What is the multiple-realizability argument?: Fodor argues that a higher-level property such as 'being in pain' or 'being money' can be realized by indefinitely many distinct physical states. Because there is no single physical kind to identify it with, the higher-level generalization cannot be reduced to a law of physics, supporting the autonomy of the special sciences.