Functionalism

Functionalism holds that what makes a state a mental state is its causal role, not the physical stuff that realizes it.

Definition

Functionalism is the view that mental states are individuated by their functional roles, that is, by their causal relations to sensory inputs, behavioral outputs, and other mental states, rather than by their underlying physical realization.

Scope

This topic covers functionalism as a theory of the nature of mental states: machine-state, analytic (common-sense), and psychofunctionalist variants, the role of multiple realizability in motivating it, and the standard objections of absent and inverted qualia, the Chinese room, and the China-brain thought experiment.

Core questions

• What individuates a mental state if not its physical composition?
• How does functionalism accommodate the multiple realizability of mental states?
• Can a functional duplicate of a person lack conscious experience?
• Does functionalism leave out the qualitative character of experience?

Key concepts

• causal role
• multiple realizability
• Ramsey sentence
• absent qualia
• inverted qualia
• China-brain

Key theories

Machine-state functionalism

Mental states are like the states of a Turing machine, defined by their transitions among inputs, outputs, and other states, so the same psychology can run on different hardware.

Analytic functionalism

Mental terms are implicitly defined by the platitudes of common-sense psychology, with mental states being whatever occupies the causal roles those platitudes specify.

History

Functionalism emerged in the 1960s from Putnam's analogy between minds and Turing machines and from Lewis's and Armstrong's causal-role analyses, offering a physicalist alternative to type identity that respects multiple realizability. Block (1978) catalogued the qualia-based objections that have framed subsequent debate over whether functional organization suffices for mentality.

Debates

Qualia objections

Whether absent-qualia and inverted-qualia scenarios show that functional duplicates can differ in or lack conscious experience.

Liberalism versus chauvinism

Whether functional specifications are pitched so abstractly that they ascribe minds to systems that lack them, or so narrowly that they exclude genuine minds.

Key figures

• Hilary Putnam
• David Lewis
• Ned Block
• Jaegwon Kim

Seminal works

• putnam1967
• lewis1972
• block1978

Frequently asked questions

How does functionalism differ from the identity theory?

The identity theory ties a mental state to a specific physical state, whereas functionalism ties it to a causal role that many different physical states could fill.