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Hilary Putnam

Analytic · North America · 1926 to 2016

American philosopher who proposed that the mind is like a program that many kinds of machine could run. Later he argued that meanings are not in the head.

What it is

Hilary Putnam (1926 to 2016) was an American philosopher, born in Chicago. He worked in the philosophy of mind, language, science and mathematics, and he took a doctorate at the University of California, Los Angeles, in 1951. He taught at Northwestern, Princeton, MIT and Harvard.

He is known for two things that seem to pull in different directions. Early on he proposed that the mind is like a program that many kinds of machine could run. Later he argued that what words mean is not settled inside the head. He was also known for changing his own mind in public.

The main ideas

  • The mind as a program. In his early work he held that a mind can be understood by what it does, the way a program can be described without saying what machine runs it. On this view, many different kinds of physical system could have minds. This is called functionalism.
  • Doubts about it. Later he came to doubt his own early view.
  • Meaning is not in the head. In a 1975 paper he argued that meanings cannot be only mental pictures or beliefs. What a word refers to in the world helps fix what it means.
  • Twin Earth. He imagined a planet just like ours, except that the clear liquid there is a different chemical, XYZ, not H2O. People on both planets hold the same beliefs about water, yet their word refers to different stuff, so it does not mean the same.
  • Realism. A theme through his career was realism, the view that statements are ordinarily true or false whatever we think. He kept revising how he put it.

What it looks like in practice

Imagine someone who uses the word water all their life without knowing what water is made of. Putnam would say that the word still refers to the real stuff in the lakes and taps, whatever the person believes about it. This is an illustration of the idea, not a passage from his writing.

Books and moments

  • 1951. He received his doctorate at UCLA under Hans Reichenbach.
  • Mathematics. With Martin Davis and Julia Robinson he did work that led to the proof that Hilbert's tenth problem, a famous question in mathematics, cannot be solved.
  • Early papers. His papers of the 1960s on minds and machines set out functionalism.
  • The Meaning of Meaning (1975) gave the Twin Earth argument.
  • Internal realism. In his middle years he argued against what he called metaphysical realism and for a view he called internal realism, which he later modified.
  • The 1960s. He took part in the antiwar movement and, for some years, belonged to the Progressive Labor Party. By the early 1970s he had moved away from it.

Questions and criticism

  • Changing positions. He often revised his views, and it is fair to ask what is left of a view that its own author gave up.
  • The mind and the program. It is fair to ask whether a description of what a mind does can leave out what it is like to have one.
  • Where meaning lives. If meaning depends on the world, it is fair to ask how a speaker can know what they mean.

Close neighbours

The pages on Saul Kripke and Willard Van Orman Quine are close neighbours in the philosophy of language and mind, and the page on Rudolf Carnap shows the logical positivism against which he argued.

Written by epchē in our own words, and checked against independent sources on 29 October 2026. The sources are listed below.

Who they connect to

Influenced

  • Jerry Fodor · He took up Putnam's view that mental states are like programs that many bodies could run.

Influenced by

  • Rudolf Carnap · He worked closely with Carnap and Reichenbach early on, and began from their view of science. (scholars disagree about this link)

Other Analytic thinkers

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