Born in Chicago, on July 31, 1926, to a father who taught Romance languages and wrote for the Daily Worker, Putnam grew up there, in France, and in Philadelphia. In the latter city, he attended Central High School and was a friend and classmate of Noam Chomsky. As an undergraduate, Putnam studied philosophy at the University of Pennsylvania and did graduate work in philosophy at Harvard University and UCLA, from which he received a Ph.D. in 1951, writing a dissertation titled The Meaning of the Concept of Probability in Application to Finite Sequences.
Putnam taught at Northwestern University (1951–1952), Princeton University (1953–1961), and MIT (1961–1965), before moving to Harvard in 1965. He was married to philosopher Ruth Anna Putnam, who taught philosophy at Wellesley College. At Harvard, Putnam was a political activist and, beginning in 1968, was the faculty advisor to the Students for a Democratic Society (SDS).
Putnam retired from teaching in 2000 but served Harvard as the Cogan University Professor Emeritus and was a founding patron of Ralston College, which has yet to open its doors. He died on March 13, 2016 at the age of eighty-nine.
Putnam is best known for his work in the philosophy of mind and, within this field, for his hypothesis of multiple realizability, which holds that mental states are distinct from and cannot be reduced to physical states. The thesis has been used both to support and attack machine-state functionalism (essentially the equivalency of the human mind and the Turing machine theoretical computer). Machine-state functionalism was an early position of Putnam’s, but he abandoned it along with other computational theories of mind by the 1980s because it failed to account for certain intuitions with respect to the externalism of mental content. It is, in fact, a hallmark of Putnam’s work that he never manifested any loyalty to a philosophical position, including his own.
Related to his work on the philosophy of mind is his work in the field of philosophy of language, especially semantic externalism, which holds that meaning does not inhere solely within the mind. He developed this in the so-called Twin Earth thought experiment. He proposed Twin Earth on which all is identical to Earth, except that its bodies of water are filled with “XYZ” as opposed to H2O. Thus, when Fredrick, a resident of Earth, uses the word water, it has a different meaning from the Twin Earth word water even as used by hisidentical twin, Frodrick. Because Fredrick and Frodrick are indistinguishable, the meaning of water cannot be determined solely by what is in their minds but must be determined with
reference to the external. Semantic externalism, it is said, triggered an “anti-subjectivist revolution” among philosophers.
In the philosophy of mathematics, Putnam collaborated with Willard Quine on the Quine–Putnam “indispensability argument” for the necessity of ontological commitments to mathematical entities. Putnam believed that mathematics, like other empirical sciences, uses strict logical proofs as well as “quasi-empirical” methods, which produce knowledge that is conjectural yet still useful in developing mathematical ideas.
As an epistemologist, Putnam developed the “brain in a vat” thought experiment, arguing against the notion that one can coherently suspect one is a disembodied brain placed in a vat by a mad scientist. The reasoning is semantic. Words refer to things and experiences. If every experience is received through wiring by a disembodied brain in a vat, the idea of “brain” held by a brain in a vat does not refer to a “real” brain within a person, since the brain in a vat has no experience of such a thing. Thus, knowledge depends on factors external to the mind and cannot be determined internally exclusively.
