Functionalism
A mental state is defined by its causal role among inputs, outputs and other states, not by its material constitution. Mind is to brain as software to hardware.
The Twentieth Century to Today · 1926 – 2016
Hilary Putnam
普特南 · Hilary Whitehall Putnam
Functionalism, Twin Earth, brains in a vat, internal realism, the entanglement of fact and value: he devised many of the central arguments of contemporary philosophy of mind and language, then criticised them himself.
Cut the pie any way you like, 'meanings' just ain't in the head!
Source: The Meaning of 'Meaning' (1975)
Putnam was born in Chicago to a writer and translator who was a Communist party member; the family lived in France during his childhood. He studied mathematics and philosophy at Pennsylvania, did graduate work at Harvard under Quine, and took his doctorate at UCLA in 1951 on probability under Reichenbach. He taught at Northwestern, Princeton and MIT, and from 1965 to his retirement in 2000 at Harvard. In the 1960s he was a radical anti-war activist and joined the Maoist Progressive Labor Party, leaving in the 1970s; he later turned to religion and was an observant Jew in his last decades.
'Minds and Machines' (1960) proposed functionalism: mental states are not brain states but functional states, defined like the states of a Turing machine by inputs, outputs and transitions, so that the same mental state can be realised in different physical systems. The theory dominated the philosophy of mind and cognitive science thereafter, and in Representation and Reality (1988) he refuted it himself. In the philosophy of mathematics he and Quine advanced the 'indispensability argument': mathematical objects exist because our best scientific theories cannot do without them.
'The Meaning of "Meaning"' (1975) introduced the Twin Earth thought experiment: suppose a planet exactly like Earth except that its 'water' is a liquid with the chemical composition XYZ; an Earthling and a Twin Earthling in 1750 are in identical psychological states, yet their word 'water' refers to different things, so 'meanings just ain't in the head', and meaning is fixed partly by the environment and by a 'division of linguistic labour' among experts. This externalism transformed the philosophy of language and of mind.
Reason, Truth and History (1981) opens with the brain in a vat: if you were a brain kept in a vat by an evil scientist and stimulated by a computer, could you think 'I am a brain in a vat'? He argued not, since your word 'vat' could not refer to real vats. The book proposed internal realism against the God's-eye view of 'metaphysical realism'. He kept revising his positions, abandoning internal realism in the 1990s for a 'common-sense realism' and pragmatism, and The Collapse of the Fact/Value Dichotomy (2002) argued that evaluation and description are inseparable in 'thick' concepts. Called 'the philosopher who changes his mind', he said it was philosophers who never changed their minds who should be suspected. He died of mesothelioma in 2016.
Key Ideas
Meanings ain't in the head
Twin Earth shows that two people in identical psychological states can mean different things by the same word. Meaning is fixed partly by the external world and the linguistic community.
Brains in a vat
The sceptical hypothesis refutes itself: if we really were brains in a vat, our words could not refer to vats, so 'I am a brain in a vat' could not be true.
Internal realism
No God's-eye view can compare our theories with 'unconceptualised reality'. Truth is rational acceptability under ideal conditions, which does not mean anything goes.
The entanglement of fact and value
Concepts like 'cruel' and 'brave' describe and evaluate at once and cannot be split into a factual and an evaluative part. Science itself depends on epistemic values such as coherence and simplicity.
Influenced by
- W. V. O. Quine
- Rudolf Carnap
In the 1950s he was Carnap's assistant and one of his earliest critics: the analytic–synthetic distinction is not simply wrong, but matters both much more and much less than Carnap thought.
- Immanuel Kant
'Internal realism' claimed Kantian descent: there is no God's-eye view, truth is idealised rational acceptability, yet this is not relativism.
- Ludwig Wittgenstein
- William James
In his last decades he returned to pragmatism, saying James and Dewey had long seen that fact and value cannot be separated and that philosophy cannot be done from the spectator's standpoint.
- John Dewey
- Saul Kripke
The two arrived almost simultaneously at the causal theory of reference for natural-kind terms; 'Twin Earth' is his version: water is H2O here and XYZ on Twin Earth, and the two are not the same word.
- Aristotle