Internal realism

Hilary Putnam
Born	Hilary Whitehall Putnam (1926-07-31)July 31, 1926 Chicago, Illinois, U.S.
Died	March 13, 2016(2016-03-13) (aged 89) Arlington, Massachusetts, U.S.
Alma mater	University of Pennsylvania Harvard University UCLA
Spouse(s)	Ruth Anna Jacobs
Awards	Rolf Schock Prizes in Logic and Philosophy (2011), Nicholas Rescher Prize for Systematic Philosophy (2015)
Era	20th-century philosophy
Region	Western philosophy
School	Analytic Pragmatism
Main interests	Philosophy of mind Philosophy of language Philosophy of science Philosophy of mathematics Metaphilosophy Epistemology
Notable ideas	Multiple realizability Functionalism Causal theory of reference Semantic externalism Brain in a vat · Twin Earth Internal realism Quine–Putnam indispensability thesis Kreisel–Putnam logic Davis–Putnam algorithm Rietdijk–Putnam argument
Influences W.V.O. Quine, John Dewey, Hans Reichenbach, Alan Turing, Immanuel Kant, Nelson Goodman, Charles Sanders Peirce, William James, Ludwig Wittgenstein, Søren Kierkegaard, Karl Marx, Sigmund Freud, Edmund Husserl,Saul Kripke
Influenced Jerry Fodor, Ned Block, Tyler Burge, David Marr, Daniel Dennett, David Lewis, Saul Kripke, Donald Davidson, George Boolos, Richard Boyd, Hartry Field, Martha Nussbaum, John Worrall

Hilary Whitehall Putnam (July 31, 1926 – March 13, 2016) was an American philosopher, mathematician, and computer scientist, and a major figure in analytic philosophy in the second half of the 20th century. He made significant contributions to philosophy of mind, philosophy of language, philosophy of mathematics, and philosophy of science. At the time of his death, Putnam was Cogan University Professor Emeritus at Harvard University.

He was known for his willingness to apply an equal degree of scrutiny to his own philosophical positions as to those of others, subjecting each position to rigorous analysis until he exposed its flaws. As a result, he acquired a reputation for frequently changing his own position.

In philosophy of mind, Putnam is known for his argument against the type-identity of mental and physical states based on his hypothesis of the multiple realizability of the mental, and for the concept of functionalism, an influential theory regarding the mind–body problem. In philosophy of language, along with Saul Kripke and others, he developed the causal theory of reference, and formulated an original theory of meaning, introducing the notion of semantic externalism based on a famous thought experiment called Twin Earth.

In philosophy of mathematics, he and his mentor W. V. Quine developed the "Quine–Putnam indispensability thesis", an argument for the reality of mathematical entities, later espousing the view that mathematics is not purely logical, but "quasi-empirical". In the field of epistemology, he is known for his critique of the well known "brain in a vat" thought experiment. This thought experiment appears to provide a powerful argument for epistemological skepticism, but Putnam challenges its coherence.