Hilary Putnam

Hilary Whitehall Putnam (1926 - 2016) was an American philosopher, mathematician, and computer scientist widely regarded as one of the most influential analytic philosophers of the second half of the twentieth century.^[1] His work reshaped the philosophy of mind, language, and mathematics, and he became known both for landmark ideas such as functionalism and semantic externalism and for his readiness to reconsider his own views.

Early life and education

Hilary Putnam was born on July 31, 1926, in Chicago, the son of the writer and translator Samuel Putnam. He spent part of his childhood in France before his family returned to the United States and settled in Philadelphia, where he attended Central High School.^[1] He studied philosophy and mathematics at the University of Pennsylvania and pursued graduate study at Harvard University before completing his doctorate at the University of California, Los Angeles, in 1951, where he worked under the logical empiricist Hans Reichenbach.^[2]

Academic career

Putnam taught at Northwestern University, Princeton University, and the Massachusetts Institute of Technology before joining the faculty of Harvard University in 1965. He remained at Harvard for the rest of his career, ultimately becoming Cogan University Professor Emeritus. For several decades he was among the most widely discussed philosophers in the English-speaking world, known as much for the breadth of his interests as for his willingness to revise his own positions.^[2]

Philosophy of mind and language

In the philosophy of mind, Putnam helped develop functionalism, the view that mental states are individuated by their functional or computational roles rather than by their physical composition. His argument from multiple realizability held that the same mental state could be realized in different physical systems, a claim that became central to later debates about the mind.^[1]

In the philosophy of language, his "Twin Earth" thought experiment argued that the meaning of natural-kind terms depends in part on the external world and on the linguistic community, not solely on the contents of a speaker's mind. This position, known as semantic externalism, is often summarized by his own phrase:

He also formulated the influential "brain in a vat" argument, which he used to challenge radical skepticism about knowledge of the external world.^[2]

Logic and mathematics

Putnam made lasting contributions to logic and computer science. With Martin Davis he devised the Davis-Putnam algorithm, a foundational procedure for testing the satisfiability of logical formulas that underlies much later work in automated reasoning. He also worked, alongside Davis and Julia Robinson, on Hilbert's tenth problem; their results contributed to the theorem, completed by Yuri Matiyasevich, showing that no general algorithm can determine whether an arbitrary Diophantine equation has integer solutions.^[1] In the philosophy of mathematics he is associated, with W. V. O. Quine, with the indispensability argument for mathematical realism.

Later thought and legacy

Putnam was noted for repeatedly changing his mind on fundamental questions, moving from a metaphysical realism to a position he called internal realism and later toward pragmatism and a form of direct realism. His later work also engaged with ethics, a critique of the fact-value dichotomy, and Jewish philosophy.^[2] He received the Rolf Schock Prize in Logic and Philosophy, the Nicholas Rescher Prize for Systematic Philosophy, and the Lauener Prize, among other honors. Putnam died on March 13, 2016, in Arlington, Massachusetts, and is remembered as one of the defining figures of twentieth-century analytic philosophy.^[3]