Function may miss felt quality
A system could appear to share the same causal organisation while critics still doubt that it has the same conscious experience.
Contemporary philosophy · 1926–2016
Putnam
Putnam repeatedly tests whether mind, meaning and truth can be confined inside an individual, using machines, Twin Earth and sceptical scenarios to force the question.
Hilary Putnam was an American philosopher who made major contributions to philosophy of mind, language, science, mathematics and ethics. His views changed substantially across his career, but his arguments for multiple realisability and semantic externalism remain central to contemporary debate.
MindKnowledge
The question he enters
The question Putnam enters
Could two internally identical thinkers mean different things because they live in different environments?
The central move
Move meaning and mind beyond the skull
Putnam argues that a mental state may be identified by the causal role it plays rather than by one biological material, allowing multiple physical realisations. His Twin Earth argument then shows that what words and thoughts refer to can depend on relations with an environment and linguistic community.
Key ideas
Terms that carry the argument.
- Functionalism
- The view that mental states are characterised by their roles among inputs, other states and behaviour.
- Multiple realisability
- The same mental role could in principle be realised by different biological or artificial physical systems.
- Semantic externalism
- The content and reference of thought depend partly on relations beyond the thinker's internal condition.
- Twin Earth
- A thought experiment in which internal duplicates refer differently because their watery environments have different underlying substances.
Where the view strains
Objections and limits.
Externalism complicates self-knowledge
If content depends on facts outside the thinker, it is difficult to explain how people know their own thoughts without investigating those facts.
Sources and routes
Read the work. Follow the argument.
Primary texts
Where to meet the position.
- Cambridge CoreThe Nature of Mental StatesWebThe multiple-realisability argument and an influential functionalist account of mind.Chapter in Philosophical Papers, Volume 2: Mind, Language and Reality, Cambridge University Press. · Official publisher chapter record; full access may require an institution or purchase. Checked Aug 2026.
- Cambridge CoreThe Meaning of 'Meaning'WebTwin Earth and the externalist claim that meanings are not simply in the head.Chapter 12 in Philosophical Papers, volume 2: Mind, Language and Reality, Cambridge University Press; pages 215-271; DOI 10.1017/CBO9780511625251.014. · Official publisher chapter record with institutional access; bibliographic or sample-only without a subscription. Checked Aug 2026.
- Open LibraryReason, Truth and HistoryWebInternal realism, brains in vats and criticism of metaphysical realism.Work-level library catalogue record for Reason, truth, and history; select a listed edition on the record. · Bibliographic record with edition, library-location, borrowing or preview links where available; this row is bibliographic or sample-only unless the selected edition states otherwise. Checked Aug 2026.
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