Hilary Putnam in the context of "Belief systems"

In logic and computer science, the Davis–Putnam algorithm was developed by Martin Davis and Hilary Putnam for checking the validity of a first-order logic formula using a resolution-based decision procedure for propositional logic. Since the set of valid first-order formulas is recursively enumerable but not recursive, there exists no general algorithm to solve this problem. Therefore, the Davis–Putnam algorithm only terminates on valid formulas. Today, the term "Davis–Putnam algorithm" is often used synonymously with the resolution-based propositional decision procedure (Davis–Putnam procedure) that is actually only one of the steps of the original algorithm.

Twin Earth is a thought experiment proposed by philosopher Hilary Putnam in his papers "Meaning and Reference" (1973) and "The Meaning of 'Meaning'" (1975). It is meant to serve as an illustration of his argument for semantic externalism, or the view that the meanings of words are not purely psychological. The Twin Earth thought experiment was one of three examples that Putnam offered in support of semantic externalism, the other two being what he called the Aluminum-Molybdenum case and the Beech-Elm case. Since the publication of these cases, numerous variations on the thought experiment have been proposed by philosophers.

Willard Van Orman Quine (/kwaɪn/ KWYNE; known to his friends as "Van"; June 25, 1908 – December 25, 2000) was an American philosopher and logician in the analytic tradition, recognized as "one of the most influential philosophers of the twentieth century". He was the Edgar Pierce Chair of Philosophy at Harvard University from 1956 to 1978.

Quine was a teacher of logic and set theory. He was famous for his position that first-order logic is the only kind worthy of the name, and developed his own system of mathematics and set theory, known as New Foundations. In the philosophy of mathematics, he and his Harvard colleague Hilary Putnam developed the Quine–Putnam indispensability argument, an argument for the reality of mathematical entities. He was the main proponent of the view that philosophy is not conceptual analysis, but continuous with science; it is the abstract branch of the empirical sciences. This led to his famous quip that "philosophy of science is philosophy enough". He led a "systematic attempt to understand science from within the resources of science itself" and developed an influential naturalized epistemology that tried to provide "an improved scientific explanation of how we have developed elaborate scientific theories on the basis of meager sensory input". He also advocated holism in science, known as the Duhem–Quine thesis.