Hilary Putnam

Putnam was born in Chicago, Illinois, in 1926. His father, Samuel Putnam, was a scholar of Romance languages, columnist, and translator who wrote for the Daily Worker, a publication of the American Communist Party, from 1936 to 1946 (when he became disillusioned with communism).[26] As a result of his father's commitment to communism, Putnam had a secular upbringing, although his mother, Riva, was Jewish.[11] The family lived in France until 1934, when they returned to the United States, settling in Philadelphia.[11] Putnam attended Central High School; there he met Noam Chomsky, who was a year behind him. The two remained friends—and often intellectual opponents—for the rest of Putnam's life.[27] Putnam studied philosophy at the University of Pennsylvania, receiving his B.A. degree and becoming a member of the Philomathean Society, the country's oldest continually existing collegiate literary society.[11][28] He did graduate work in philosophy at Harvard University[11] and later at UCLA'S philosophy department, where he received his Ph.D. in 1951 for his dissertation, The Meaning of the Concept of Probability in Application to Finite Sequences.[29] Putnam's dissertation supervisor Hans Reichenbach was a leading figure in logical positivism, the dominant school of philosophy of the day; one of Putnam's most consistent positions has been his rejection of logical positivism as self-defeating.[28]

After teaching at Northwestern University (1951–52), Princeton University (1953–61), and MIT (1961–65), Putnam moved to Harvard in 1965. His wife, the philosopher Ruth Anna Putnam, took a teaching position in philosophy at Wellesley College.[28] Hilary and Ruth Anna were married on August 11, 1962.[30] Ruth Anna, descendant of a family with a long scholarly tradition in Gotha (her ancestor was the German classical scholar Christian Friedrich Wilhelm Jacobs),[31] was born in Berlin, Germany,[32] in 1927 to anti-Nazi activist parents and, like Putnam, was raised atheist (her mother was Jewish and her father from a Christian background).[33][34][35][36] The Putnams, rebelling against the antisemitism they experienced during their youth, decided to establish a traditional Jewish home for their children.[33] Since they had no experience with the rituals of Judaism, they sought out invitations to other Jews' homes for Seder. They had "no idea how to do it [themselves]", in Ruth Anna's words. They began to study Jewish ritual and Hebrew, and became more Jewishly interested, identified, and active. In 1994, Hilary Putnam celebrated a belated Bar Mitzvah service. His wife had a Bat Mitzvah service four years later.[33]

Putnam was a popular teacher at Harvard. In keeping with his family tradition, he was politically active.[28] In the 1960s and early 1970s, he was an active supporter of the American Civil Rights Movement and opposition to the Vietnam War.[25] In 1963, he organized one of MIT's first faculty and student committees against the war. Putnam was disturbed when he learned from David Halberstam's reports that the U.S. was "defending" South Vietnamese peasants from the Vietcong by poisoning their rice crops.[28] After moving to Harvard in 1965, he organized campus protests and began teaching courses on Marxism. Putnam became an official faculty advisor to the Students for a Democratic Society and in 1968 a member of the Progressive Labor Party (PLP).[28] He was elected a Fellow of the American Academy of Arts and Sciences in 1965.[37] After 1968, his political activities centered on the PLP.[25] The Harvard administration considered these activities disruptive and attempted to censure Putnam, but two other faculty members criticized the procedures.[38][39] Putnam permanently severed his ties with the PLP in 1972.[40] In 1997, at a meeting of former draft resistance activists at Boston's Arlington Street Church, he called his involvement with the PLP a mistake. He said he had been impressed at first with the PLP's commitment to alliance-building and its willingness to attempt to organize from within the armed forces.[25]

In 1976, Putnam was elected president of the American Philosophical Association. The next year, he was selected as Walter Beverly Pearson Professor of Mathematical Logic in recognition of his contributions to the philosophy of logic and mathematics.[28] While breaking with his radical past, Putnam never abandoned his belief that academics have a particular social and ethical responsibility toward society. He continued to be forthright and progressive in his political views, as expressed in the articles "How Not to Solve Ethical Problems" (1983) and "Education for Democracy" (1993).[28]

Putnam was a Corresponding Fellow of the British Academy. He retired from teaching in June 2000, but as of 2009 continued to give a seminar almost yearly at Tel Aviv University. He also held the Spinoza Chair of Philosophy at the University of Amsterdam in 2001.[41] He was the Cogan University Professor Emeritus at Harvard University and a founding patron of the small liberal arts college Ralston College. His corpus includes five volumes of collected works, seven books, and more than 200 articles. Putnam's renewed interest in Judaism inspired him to publish several books and essays on the topic.[42] With his wife, he co-authored several books and essays on the late-19th-century American pragmatist movement.[28]

For his contributions in philosophy and logic, Putnam was awarded the Rolf Schock Prize in 2011[43] and the Nicholas Rescher Prize for Systematic Philosophy in 2015.[44] He delivered his last Skype talk, "Thought and Language," at an international conference on "The Philosophy of Hilary Putnam" held at the Indian Institute of Technology, Bombay, on October 3, 2015, organized by his student Sanjit Chakraborty.[45][46] Putnam died at his home in Arlington, Massachusetts, on March 13, 2016.[47]

Putnam made a significant contribution to philosophy of mathematics in the Quine–Putnam "indispensability argument" for mathematical realism.[59] Stephen Yablo considers this argument one of the most challenging in favor of the existence of abstract mathematical entities, such as numbers and sets.[60] The form of the argument is as follows.

1. One must have ontological commitments to all entities that are indispensable to the best scientific theories, and to those entities only (commonly referred to as "all and only").
2. Mathematical entities are indispensable to the best scientific theories. Therefore,
3. One must have ontological commitments to mathematical entities.[61]

The justification for the first premise is the most controversial. Both Putnam and Quine invoke naturalism to justify the exclusion of all non-scientific entities, and hence to defend the "only" part of "all and only". The assertion that "all" entities postulated in scientific theories, including numbers, should be accepted as real is justified by confirmation holism. Since theories are not confirmed in a piecemeal fashion, but as a whole, there is no justification for excluding any of the entities referred to in well-confirmed theories. This puts the nominalist who wishes to exclude the existence of sets and non-Euclidean geometry but include the existence of quarks and other undetectable entities of physics, for example, in a difficult position.[61]

Putnam holds the view that mathematics, like physics and other empirical sciences, uses both strict logical proofs and "quasi-empirical" methods. For example, Fermat's last theorem states that for no integer ${\displaystyle n>2}$ are there positive integer values of x, y, and z such that ${\displaystyle x^{n}+y^{n}=z^{n}}$. Before Andrew Wiles proved this for all ${\displaystyle n>2}$ in 1995,[62] it had been proved for many values of n. These proofs inspired further research in the area, and formed a quasi-empirical consensus for the theorem. Even though such knowledge is more conjectural than a strictly proved theorem, it was still used in developing other mathematical ideas.[16]

Putnam has contributed to scientific fields not directly related to his work in philosophy.[8] As a mathematician, he contributed to the resolution of Hilbert's tenth problem in mathematics. This problem (now known as Matiyasevich's theorem or the MRDP theorem) was settled by Yuri Matiyasevich in 1970, with a proof that relied heavily on previous research by Putnam, Julia Robinson and Martin Davis.[63]

In computability theory, Putnam investigated the structure of the ramified analytical hierarchy, its connection with the constructible hierarchy and its Turing degrees. He showed that there are many levels of the constructible hierarchy that add no subsets of the integers[64] and later, with his student George Boolos, that the first such "non-index" is the ordinal ${\displaystyle \beta _{0}}$ of ramified analysis[65] (this is the smallest ${\displaystyle \beta }$ such that ${\displaystyle L_{\beta }}$ is a model of full second-order comprehension), and also, together with a separate paper with Richard Boyd (another of Putnam's students) and Gustav Hensel,[66] how the Davis–Mostowski–Kleene hyperarithmetical hierarchy of arithmetical degrees can be naturally extended up to ${\displaystyle \beta _{0}}$.

In computer science, Putnam is known for the Davis–Putnam algorithm for the Boolean satisfiability problem (SAT), developed with Martin Davis in 1960.[8] The algorithm finds whether there is a set of true or false values that satisfies a given Boolean expression so that the entire expression becomes true. In 1962, they further refined the algorithm with the help of George Logemann and Donald W. Loveland. It became known as the DPLL algorithm. It is efficient and still forms the basis of most complete SAT solvers.[9]

A "brain in a vat"—Putnam uses this thought experiment to argue that skeptical scenarios are impossible.

In epistemology, Putnam is known for his "brain in a vat" thought experiment (a modernized version of Descartes's evil demon hypothesis). The argument is that one cannot coherently suspect that one is a disembodied "brain in a vat" placed there by some "mad scientist".[17]

This follows from the causal theory of reference. Words always refer to the kinds of things they were coined to refer to, the kinds of things their user, or the user's ancestors, experienced. So, if some person, Mary, is a "brain in a vat", whose every experience is received through wiring and other gadgetry created by the mad scientist, then Mary's idea of a brain does not refer to a real brain, since she and her linguistic community have never encountered such a thing. To her a brain is actually an image fed to her through the wiring. Nor does her idea of a vat refer to a real vat. So if, as a brain in a vat, she says, "I'm a brain in a vat", she is actually saying, "I'm a brain-image in a vat-image", which is incoherent. On the other hand, if she is not a brain in a vat, then saying that she is a brain in a vat is still incoherent, because she actually means the opposite. This is a form of epistemological externalism: knowledge or justification depends on factors outside the mind and is not solely determined internally.[17]

Putnam has clarified that his real target in this argument was never skepticism, but metaphysical realism.[67][68] Since realism of this kind assumes the existence of a gap between how one conceives the world and the way the world really is, skeptical scenarios such as this one (or Descartes's evil demon) present a formidable challenge. By arguing that such a scenario is impossible, Putnam attempts to show that this notion of a gap between one's concept of the world and the way it is is absurd. One cannot have a "God's-eye" view of reality. One is limited to one's conceptual schemes, and metaphysical realism is therefore false.[69]

In the late 1970s and the 1980s, stimulated by results from mathematical logic and by some of Quine's ideas, Putnam abandoned his long-standing defence of metaphysical realism—the view that the categories and structures of the external world are both causally and ontologically independent of the conceptualizations of the human mind. He adopted a rather different view, which he called "internal realism"[70][18] or "pragmatic realism".[71]

Internal realism is the view that, although the world may be causally independent of the human mind, the world's structure—its division into kinds, individuals and categories—is a function of the human mind, and hence the world is not ontologically independent. The general idea is influenced by Immanuel Kant's idea of the dependence of our knowledge of the world on the categories of thought.[72]

The problem with metaphysical realism, according to Putnam, is that it fails to explain the possibility of reference and truth.[73]^:331 According to the metaphysical realist, our concepts and categories refer because they match up in some mysterious manner with the categories, kinds and individuals inherent in the external world. But how is it possible that the world "carves up" into certain structures and categories, the mind carves up the world into its own categories and structures, and the two carvings perfectly coincide? The answer must be that the world does not come pre-structured but that the human mind and its conceptual schemes impose structure on it. In Reason, Truth, and History, Putnam identified truth with what he termed "idealized rational acceptability." The theory, which owes something to C. S. Peirce, is that a belief is true if it would be accepted by anyone under ideal epistemic conditions.[18]

Nelson Goodman formulated a similar notion in Fact, Fiction and Forecast (1956). "We have come to think of the actual as one among many possible worlds. We need to repaint that picture. All possible worlds lie within the actual one", Goodman wrote.[74]^:57 Putnam rejected this form of social constructivism, but retained the idea that there can be many correct descriptions of reality. None of these descriptions can be scientifically proven to be the "one, true" description of the world. For Putnam, this does not imply relativism, because not all descriptions are equally correct and correctness is not determined subjectively.[75]

Putnam renounced internal realism in his reply to Simon Blackburn in the volume Reading Putnam.[76] The reasons he gave up his "antirealism" are stated in the first three of his replies in "The Philosophy of Hilary Putnam", an issue of the journal Philosophical Topics, where he gives a history of his use(s) of the term "internal realism", and, at more length, in his The Threefold Cord: Mind, Body and World (1999).[77]

Although he abandoned internal realism, Putnam still resisted the idea that any given thing or system of things can be described in exactly one complete and correct way. He thus accepts "conceptual relativity"—the view that it may be a matter of choice or convention, e.g., whether mereological sums exist, or whether spacetime points are individuals or mere limits. In other words, having abandoned internal realism, Putnam came to accept metaphysical realism in the broad sense of rejecting all forms of verificationism and all talk of our "making" the world.[78]

Under the influence of Peirce and William James, Putnam also became convinced that there is no fact–value dichotomy; that is, normative (e.g., ethical and aesthetic) judgments often have a factual basis, while scientific judgments have a normative element.[75]

At the end of the 1980s, Putnam became increasingly disillusioned with what he perceived as the "scientism" and the rejection of history that characterize modern analytic philosophy. He rejected internal realism because it assumed a "cognitive interface" model of the relation between the mind and the world. Putnam claimed that the very notion of truth would have to be abandoned by a consistent eliminative materialist.[79] Under the increasing influence of James and the pragmatists, he adopted a direct realist view of this relation.[80] For a time, under the influence of Ludwig Wittgenstein, he adopted a pluralist view of philosophy itself and came to view most philosophical problems as nothing more than conceptual or linguistic confusions created by philosophers by using ordinary language out of context.[75] A book of articles on pragmatism by Ruth Anna Putnam and Hilary Putnam, Pragmatism as a Way of Life: The Lasting Legacy of William James and John Dewey (Harvard UP, ISBN 9780674967502), edited by David Macarthur, was published in 2017.[81]

Many of Putnam's last works addressed the concerns of ordinary people, particularly social problems.[82] For example, he wrote about the nature of democracy, social justice and religion. He also discussed Jürgen Habermas's ideas, and wrote articles influenced by continental philosophy.[28]

Putnam himself may be his own most formidable philosophical adversary:[14] his frequent changes of mind have led him to attack his previous positions. But many significant criticisms of his views have come from other philosophers and scientists. For example, multiple realizability has been criticized on the grounds that, if it were true, research and experimentation in the neurosciences would be impossible.[83] According to William Bechtel and Jennifer Mundale, to be able to conduct such research in the neurosciences, universal consistencies must either exist or be assumed to exist in brain structures. It is the similarity (or homology) of brain structures that allows us to generalize across species.[83] If multiple realizability were an empirical fact, results from experiments conducted on one species of animal (or one organism) would not be meaningful when generalized to explain the behavior of another species (or organism of the same species).[84] Jaegwon Kim, David Lewis, Robert Richardson and Patricia Churchland have also criticized metaphysical realism.[85][86][87][88]

Putnam himself formulated one of the main arguments against functionalism: the Twin Earth thought experiment. But there have been other criticisms. John Searle's Chinese room argument (1980) is a direct attack on the claim that thought can be represented as a set of functions. The thought experiment is designed to show that it is possible to mimic intelligent action with a purely functional system, without any interpretation or understanding. Searle describes a situation in which a person who speaks only English is locked in a room with Chinese symbols in baskets and a rule book in English for moving the symbols around. The person is instructed, by people outside the room, to follow the rule book for sending certain symbols out of the room when given certain symbols. The people outside the room speak Chinese and are communicating with the person inside via the Chinese symbols. According to Searle, it would be absurd to claim that the English speaker inside "knows" Chinese based on these syntactic processes alone. This argument attempts to show that systems that operate merely on syntactic processes cannot realize any semantics (meaning) or intentionality (aboutness). Searle thus attacks the idea that thought can be equated with following a set of syntactic rules and concludes that functionalism is an inadequate theory of the mind.[89] Ned Block has advanced several other arguments against functionalism.[90]

Despite the many changes in his other positions, Putnam consistently adhered to semantic holism. Michael Dummett, Jerry Fodor, Ernest Lepore, and others have identified problems with this position. In the first place, they suggest that, if semantic holism is true, it is impossible to understand how a speaker of a language can learn the meaning of an expression in the language. Given the limits of our cognitive abilities, we will never be able to master the whole of the English (or any other) language, even based on the (false) assumption that languages are static and immutable entities. Thus, if one must understand all of a natural language to understand a single word or expression, language learning is simply impossible. Semantic holism also fails to explain how two speakers can mean the same thing when using the same expression, and therefore how any communication is possible between them. Given a sentence P, since Fred and Mary have each mastered different parts of the English language and P is related in different ways to the sentences in each part, P means one thing to Fred and something else to Mary. Moreover, if P derives its meaning from its relations with all the sentences of a language, as soon as the vocabulary of an individual changes by the addition or elimination of a sentence, the totality of relations changes, and therefore also the meaning of P. As this is a common phenomenon, the result is that P has two different meanings in two different moments in the life of the same person. Consequently, if I accept the truth of a sentence and then reject it later on, the meaning of what I rejected and what I accepted are completely different and therefore I cannot change my opinions with regard to the same sentences.[91][92][93]

Putnam's brain in a vat argument has also been criticized.[94] Crispin Wright argues that Putnam's formulation of the brain-in-a-vat scenario is too narrow to refute global skepticism. The possibility that one is a recently disembodied brain in a vat is not undermined by semantic externalism. If a person has lived her entire life outside the vat—speaking the English language and interacting normally with the outside world—prior to her "envatment" by a mad scientist, when she wakes up inside the vat, her words and thoughts (e.g., "tree" and "grass") will still refer to the objects or events in the external world that they referred to before her envatment.[68] In another scenario, a brain in a vat may be hooked up to a supercomputer that randomly generates perceptual experiences. In that case, one's words and thoughts would not refer to anything: semantics would no longer exist and the argument would be meaningless.[95]

In philosophy of mathematics, Stephen Yablo has argued that the Quine–Putnam indispensability thesis does not demonstrate that mathematical entities are truly indispensable. The argumentation is sophisticated, but the upshot is that one can achieve the same logical results by simply adding to any statement about an abstract object the assumption "so-and-so is assumed (or hypothesized) to exist". For example, one can take the argument for indispensability described above and adjust it as follows:

1*. One must have ontological commitments to all and only the [abstract] entities for which, under the assumption that they exist, their existence is indispensable to the best scientific theories.

2*. Under the assumption that they exist, the existence of mathematical entities is indispensable to the best scientific theories. Therefore,

3*. Under the assumption that mathematical entities exist, one must have ontological commitments to the existence of mathematical entities.[60]

Finally, Curtis Brown has criticized Putnam's internal realism as a disguised form of subjective idealism, in which case it is subject to the traditional arguments against that position. In particular, it falls into the trap of solipsism. That is, if existence depends on experience, as subjective idealism maintains, and if one's consciousness ceased to exist, then the rest of the universe would also cease to exist.[72]

Vincent C. Müller compiled a detailed bibliography of Putnam's writings, citing 16 books and 198 articles, published in 1993 in PhilPapers.[96]

• Philosophy of Mathematics: Selected Readings. Edited with Paul Benacerraf. Englewood Cliffs, N.J.: Prentice-Hall, 1964. 2nd ed., Cambridge: Cambridge University Press, 1983. ISBN 0-521-29648-X
• "The 'Innateness Hypothesis' and Explanatory Models in Linguistics", Synthese, Vol. 17, No. 1, March 1967, pp. 12–22.
• Philosophy of Logic. New York: Harper & Row, 1971. London: George Allen & Unwin, 1972. ISBN 0-04-160009-6
• Mathematics, Matter and Method. Philosophical Papers, vol. 1. Cambridge: Cambridge University Press, 1975. 2nd. ed., 1985 paperback: ISBN 0-521-29550-5
• Mind, Language and Reality. Philosophical Papers, vol. 2. Cambridge: Cambridge University Press, 1975. 2003 paperback: ISBN 0-521-29551-3
• Meaning and the Moral Sciences. London: Routledge and Kegan Paul, 1978.
• Reason, Truth, and History. Cambridge: Cambridge University Press, 1981. 2004 paperback: ISBN 0-521-29776-1
• Realism and Reason. Philosophical Papers, vol. 3. Cambridge: Cambridge University Press, 1983. 2002 paperback: ISBN 0-521-31394-5
• Methodology, Epistemology, and Philosophy of Science: Essays in Honour of Wolfgang Stegmüller. edited with Wilhelm K. Essler and Carl G. Hempel. Dordrecht: D. Reidel, 1983.
• Epistemology, Methodology, and Philosophy of Science: Essays in Honour of Carl G. Hempel. edited with Wilhelm K. Essler and Wolfgang Stegmüller. Dordrecht: D. Reidel, 1985.
• The Many Faces of Realism. La Salle, Ill.: Open Court, 1987. ISBN 0-8126-9043-5
• Representation and Reality. Cambridge, Massachusetts: MIT Press, 1988. ISBN 0-262-66074-1
• Realism with a Human Face. edited by J. F. Conant. Cambridge, Massachusetts: Harvard University Press, 1990. 9780674749450 Description. ISBN 0-674-74945-6
• Renewing Philosophy. Cambridge, Massachusetts: Harvard University Press, 1992. 9780674760943 Description. ISBN 0-674-76094-8
• Pursuits of Reason: Essays in Honor of Stanley Cavell. edited with Ted Cohen and Paul Guyer. Lubbock: Texas Tech University Press, 1993. ISBN 0-89672-266-X
• Words and Life. edited by J. F. Conant. Cambridge, Massachusetts: Harvard University Press, 1994. 9780674956070 Description. ISBN 0-674-95607-9
• Pragmatism: An Open Question. Oxford: Blackwell, 1995. ISBN 0-631-19343-X
• The Threefold Cord: Mind, Body, and World. New York: Columbia University Press, 1999. ISBN 0-231-10287-9
• Enlightenment and Pragmatism. Assen: Koninklijke Van Gorcum, 2001. 48pp.
• The Collapse of the Fact/Value Dichotomy and Other Essays. Cambridge, Massachusetts: Harvard University Press, 2002. Description. ISBN 0-674-01380-8
• Ethics Without Ontology. Cambridge, Massachusetts: Harvard University Press, 2002. 9780674018518 Description. ISBN 0-674-01851-6
• Jewish Philosophy as a Guide to Life: Rosenzweig, Buber, Levinas, Wittgenstein. Bloomington: Indiana University Press, 2008.
• Philosophy in an Age of Science, edited by Mario De Caro and David Macarthur. Cambridge, Massachusetts: Harvard University Press, 2012. 9780674050136 Description.
• Naturalism, Realism, and Normativity, edited by Mario De Caro, Cam, Mass: Harvard University Press, 2016, ISBN 9780674659698.
• Pragmatism as a Way of Life: The Lasting Legacy of William James and John Dewey (with Ruth Anna Putnam), edited by David Macarthur, Cambridge, Mass: Harvard University Press, 2017. Description. ISBN 0-674-96750-X.

• American philosophy
• List of American philosophers
• "Is Logic Empirical?"

• Y. Ben-Menahem (ed.), Hilary Putnam, Contemporary Philosophy in Focus, Cambridge University Press, Cambridge, 2005.
• P. Clark-B. Hale (eds.), Reading Putnam, Blackwell, Cambridge (Massachusetts)-Oxford 1995.
• C. S. Hill (ed.), The Philosophy of Hilary Putnam, Fayetteville, Arkansas 1992.
• M. Rüdel, Erkenntnistheorie und Pragmatik: Untersuchungen zu Richard Rorty und Hilary Putnam (dissertation), Hamburg 1987.
• Maximilian de Gaynesford, Hilary Putnam, McGill-Queens University Press / Acumen, 2006.
• Auxier, R. E., Anderson, D. R., & Hahn, L. E., eds., The Philosophy of Hilary Putnam, The Library of Living Philosophers, Open Court, Chicago, Illinois, 2015.
• Sanjit Chakraborty, Understanding Meaning and World: A Relook on Semantic Externalism, Cambridge Scholars Publishing, London, 2016.

• Quotations related to Hilary Putnam at Wikiquote
• Hilary Putnam at PhilPapers
• Hilary Putnam at IMDb
• Hilary Putnam at the Indiana Philosophy Ontology Project
• An extensive bibliography
• An extensive directory
• Hilary Putnam at the Mathematics Genealogy Project
• London Review of Books contributor page
• Hilary Putnam: On Mind, Meaning and Reality, Interview by Josh Harlan, The Harvard Review of Philosophy, spring 1992.
• "To Think with Integrity", Hilary Putnam's Farewell Lecture, The Harvard Review of Philosophy, Spring 2000.
• Putnam, "The Fact/Value Dichotomy and its critics"; Roundtable on Externalism audio/video lecture, audio discussion, March 2007, University College Dublin.
• Hilary Putnam – Externalism: Its Motivation And Its Critics, video of a lecture, delivered at Harvard University on October 4, 2007.
• A short film about the Putnam-Rorty debate and its influence on the pragmatist revival on YouTube
• The Moscow Center for Consciousness Studies video interview with Hilary Putnam 2010-04-21 (with transcript)