Hilary Putnam

Hilary Whitehall Putnam (/ˈpʌtnəm/; July 31, 1926 – March 13, 2016) was an American philosopher, mathematician, computer scientist, and figure in analytic philosophy in the second half of the 20th century. He contributed to the studies of philosophy of mind, philosophy of language, philosophy of mathematics, and philosophy of science.^[5] Outside philosophy, Putnam contributed to mathematics and computer science. Together with Martin Davis he developed the Davis–Putnam algorithm for the Boolean satisfiability problem^[6] and he helped demonstrate the unsolvability of Hilbert's tenth problem.^[7]

Putnam applied equal scrutiny to his own philosophical positions as to those of others, subjecting each position to rigorous analysis until he exposed its flaws.^[8] As a result, he acquired a reputation for frequently changing his positions.^[9] In philosophy of mind, Putnam argued 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.^[5][10] 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 thought experiment called Twin Earth.^[11]

In

In his later work, Putnam became increasingly interested in American pragmatism, Jewish philosophy, and ethics, engaging with a wider array of philosophical traditions. He also displayed an interest in metaphilosophy, seeking to "renew philosophy" from what he identified as narrow and inflated concerns.^[17] He was at times a politically controversial figure, especially for his involvement with the Progressive Labor Party in the late 1960s and early 1970s.^[18]

Hilary Whitehall Putnam was born on July 31, 1926, in Chicago, Illinois.^[19] 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.^[20] Because of his father's commitment to communism, Putnam had a secular upbringing, although his mother, Riva, was Jewish.^[8] In early 1927, six months after Hilary's birth, the family moved to France, where Samuel was under contract to translate the surviving works of François Rabelais.^[17][19] In a 2015 autobiographical essay, Putnam said that his first childhood memories were from his life in France, and his first language was French.^[17]

Putnam completed the first two years of his

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. 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).^[22]

Putnam was a Corresponding Fellow of the British Academy. He was elected to the American Philosophical Society in 1999.^[31] He retired from teaching in June 2000, becoming Cogan University Professor Emeritus, 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.^[32] 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.^[33] With his wife, he co-authored several essays and a book on the late-19th-century American pragmatist movement.^[22]

For his contributions in philosophy and logic, Putnam was awarded the

Putnam's best-known work concerns philosophy of mind. His most noted original contributions to that field came in several key papers published in the late 1960s that set out the hypothesis of

Putnam, Jerry Fodor, and others argued that along with being an effective argument against type-identity theories, multiple realizability implies that any low-level explanation of higher-level mental phenomena is insufficiently abstract and general. Functionalism, which identifies mental kinds with functional kinds that are characterized exclusively in terms of causes and effects, abstracts from the level of microphysics, and therefore seemed to be a better explanation of the relation between mind and body. In fact, there are many functional kinds, including mousetraps and eyes, that are multiply realized at the physical level.^{[38][40][39]: 648–649 [41]: 6}

Multiple realizability has been criticized on the grounds that, if it were true, research and experimentation in the neurosciences would be impossible.

Putnam himself put forth the first formulation of such a functionalist theory. This formulation, now called "machine-state functionalism", was inspired by analogies Putnam and others made between the mind and Turing machines.^[48] The point for functionalism is the nature of the states of the Turing machine. Each state can be defined in terms of its relations to the other states and to the inputs and outputs, and the details of how it accomplishes what it accomplishes and of its material constitution are completely irrelevant. According to machine-state functionalism, the nature of a mental state is just like the nature of a Turing machine state. Just as "state one" simply is the state in which, given a particular input, such-and-such happens, so being in pain is the state which disposes one to cry "ouch", become distracted, wonder what the cause is, and so forth.^[49]

Ian Hacking called Representation and Reality (1988) a book that "will mostly be read as Putnam’s denunciation of his former philosophical psychology, to which he gave the name 'functionalism'."^[50] Writing in Noûs, Barbara Hannon described "the inventor of functionalism" as arguing "against his own former computationalist views".^[51]

Putnam's change of mind was primarily due to the difficulties computational theories have in explaining certain intuitions with respect to the externalism of mental content.^[52] This is illustrated by his Twin Earth thought experiment.^{[non-primary source needed]}

In 1988 Putnam also developed a separate argument against functionalism based on Fodor's generalized version of multiple realizability. Asserting that functionalism is really a watered-down

By 2012 Putnam accepted a modification of functionalism called "liberal functionalism". The view holds that "what matters for consciousness and for mental properties generally is the right sort of functional capacities and not the particular matter that subserves those capacities".[56] The specification of these capacities may refer to what goes on outside the organism's "brain", may include intentional idioms, and need not describe a capacity to compute something or other.^[56]

Putnam himself formulated one of the main arguments against functionalism, the Twin Earth thought experiment, though there have been additional 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. It 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. People outside the room instruct the person inside 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.^[57] Ned Block has advanced several other arguments against functionalism.^[58]

One of Putnam's contributions to philosophy of language is his semantic externalism, the claim that terms' meanings are determined by factors outside the mind, encapsulated in his slogan that "meaning just ain't in the head". His views on meaning, first laid out in Meaning and Reference (1973), then in The Meaning of "Meaning" (1975), use his "Twin Earth" thought experiment to defend this thesis.^[59][60]

Twin Earth shows this, according to Putnam, since on Twin Earth everything is identical to Earth, except that its lakes, rivers and oceans are filled with XYZ rather than H₂O. Consequently, when an earthling, Fredrick, uses the Earth-English word "water", it has a different meaning from the Twin Earth-English word "water" when used by his physically identical twin, Frodrick, on Twin Earth. Since Fredrick and Frodrick are physically indistinguishable when they utter their respective words, and since their words have different meanings, meaning cannot be determined solely by what is in their heads.^[61] This led Putnam to adopt a version of semantic externalism with regard to meaning and mental content.^[14][38] The philosopher of mind and language Donald Davidson, despite his many differences of opinion with Putnam, wrote that semantic externalism constituted an "anti-subjectivist revolution" in philosophers' way of seeing the world. Since Descartes's time, philosophers had been concerned with proving knowledge from the basis of subjective experience. Thanks to Putnam, Saul Kripke, Tyler Burge and others, Davidson said, philosophy could now take the objective realm for granted and start questioning the alleged "truths" of subjective experience.^[62]

Along with Kripke, Keith Donnellan, and others, Putnam contributed to what is known as the causal theory of reference.^[5] In particular, he maintained in The Meaning of "Meaning" that the objects referred to by natural kind terms—such as "tiger", "water", and "tree"—are the principal elements of the meaning of such terms. There is a linguistic division of labor, analogous to Adam Smith's economic division of labor, according to which such terms have their references fixed by the "experts" in the particular field of science to which the terms belong. So, for example, the reference of the term "lion" is fixed by the community of zoologists, the reference of the term "elm tree" is fixed by the community of botanists, and chemists fix the reference of the term "table salt" as sodium chloride. These referents are considered rigid designators in the Kripkean sense and are disseminated outward to the linguistic community.^{[38][63]: 33}

Putnam specifies a finite sequence of elements (a vector) for the description of the meaning of every term in the language. Such a vector consists of four components:

1. the object to which the term refers, e.g., the object individuated by the chemical formula H₂O;
2. a set of typical descriptions of the term, referred to as "the stereotype", e.g., "transparent", "colorless", and "hydrating";
3. the semantic indicators that place the object into a general category, e.g., "natural kind" and "liquid";
4. the syntactic indicators, e.g., "concrete noun" and "mass noun".

Such a "meaning-vector" provides a description of the reference and use of an expression within a particular linguistic community. It provides the conditions for its correct usage and makes it possible to judge whether a single speaker attributes the appropriate meaning to it or whether its use has changed enough to cause a difference in its meaning. According to Putnam, it is legitimate to speak of a change in the meaning of an expression only if the reference of the term, and not its stereotype, has changed.^{[17]: 339–340} But since no possible algorithm can determine which aspect—the stereotype or the reference—has changed in a particular case, it is necessary to consider the usage of other expressions of the language.^{[38][non-primary source needed]} Since there is no limit to the number of such expressions to be considered, Putnam embraced a form of semantic holism.^[64]

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 one accepts the truth of a sentence and then rejects it later on, the meaning of what one rejected and what one accepted are completely different and therefore one cannot change opinions with regard to the same sentences.^{[65][page needed][66][page needed][67][page needed]}

In the

${\displaystyle n>2}$ are there positive integer values of x, y, and z such that ${\displaystyle x^{n}+y^{n}=z^{n}}$. Before

${\displaystyle n>2}$

The Quine–Putnam indispensability argument has been extremely influential in the philosophy of mathematics, inspiring continued debate and development of the argument in contemporary philosophy of mathematics. According to the Stanford Encyclopedia of Philosophy, many in the field consider it the best argument for mathematical realism.^[12] Prominent counterarguments come from Hartry Field, who argues that mathematics is not indispensable to science, and Penelope Maddy and Elliott Sober, who dispute whether we are committed to mathematical realism even if it is indispensable to science.^[12]

Putnam has contributed to scientific fields not directly related to his work in philosophy.^[5] 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.^[73]

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.^[74] Later, with his student George Boolos, he showed that the first such "non-index" is the ordinal ${\displaystyle \beta _{0}}$ of ramified analysis^[75] (this is the smallest ${\displaystyle \beta }$ such that ${\displaystyle L_{\beta }}$ is a model of full second-order comprehension). Also, together with a separate paper with his student Richard Boyd and Gustav Hensel, he demonstrated how the Davis–Mostowski–Kleene hyperarithmetical hierarchy of arithmetical degrees can be naturally extended up to ${\displaystyle \beta _{0}}$.^[76]

In computer science, Putnam is known for the Davis–Putnam algorithm for the Boolean satisfiability problem (SAT), developed with Martin Davis in 1960.^[5] 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.^[6]

In

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.^[14][77]

Putnam has clarified that his real target in this argument was never skepticism, but

Putnam's brain in a vat argument has been criticized.^[82] 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.^[79]

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 defense of

According to Putnam, the problem with metaphysical realism is that it fails to explain the possibility of reference and truth.[87] 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.^[81] In Reason, Truth, and History, Putnam identified truth with what he termed "idealized rational acceptability." The theory is that a belief is true if it would be accepted by anyone under ideal epistemic conditions.^{[15][83]: §7.1}

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.^[88] 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. He thus accepted "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.^{[89][non-primary source needed]}

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.^[86] In his reply to Simon Blackburn in the volume Reading Putnam, Putnam renounced internal realism^[11] because it assumed a "cognitive interface" model of the relation between the mind and the world. Under the increasing influence of William James and the pragmatists, he adopted a direct realist view of this relation.^{[90][91][92]: 23–24} 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 came to accept metaphysical realism in a broader sense, rejecting all forms of verificationism and all talk of our "making" the world.^[93]

In the philosophy of perception, Putnam came to endorse direct realism, according to which perceptual experiences directly present one with the external world. He once further held that there are no mental representations, sense data, or other intermediaries between the mind and the world.^[52] By 2012, however, he rejected this commitment in favor of "transactionalism", a view that accepts both that perceptual experiences are world-involving transactions, and that these transactions are functionally describable (provided that worldly items and intentional states may be referred to in the specification of the function). Such transactions can further involve qualia.^[56][94]

During his career, Putnam espoused various positions on the

Many of Putnam's last works addressed the concerns of ordinary people, particularly social problems.[102] 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.^[22]

• Putnam, H. (1971). Philosophy of Logic. New York:
  ISBN 0-04-160009-6
  .
• Putnam, H. (1975). Mathematics, Matter and Method. Philosophical Papers, vol. 1. Cambridge: Cambridge University Press.
  ISBN 0-521-29550-5
• Putnam, H. (1975). Mind, Language and Reality. Philosophical Papers, vol. 2. Cambridge: Cambridge University Press.
  ISBN 0-521-29551-3
• Putnam, H. (1978). Meaning and the Moral Sciences. Routledge and Kegan Paul. pp. 123–140.
  OCLC 318417931
  .
• Putnam, H. (1981). Reason, Truth, and History. Cambridge University Press.
  ISBN 0-521-29776-1
• Putnam, H. (1983). Realism and Reason. Philosophical Papers, vol. 3. Cambridge: Cambridge University Press.
  ISBN 0-521-31394-5
• Putnam, H. (1987). The Many Faces of Realism. La Salle, Ill.: Open Court.
  ISBN 0-8126-9043-5
  .
• Putnam, H. (1988). Representation and Reality. Cambridge, Massachusetts: MIT Press.
  OCLC 951364040
  .
• Putnam, H. (1990).
  OCLC 1014989000
  .
• Putnam, H. (1992). Renewing Philosophy. Cambridge, Massachusetts: Harvard University Press.
  ISBN 0-674-76094-8
  .
• Putnam, H.; Cohen, Ted;
  ISBN 0-89672-266-X
  .
• Putnam, H. (1994). Conant, J. F. (ed.). Words and Life. Cambridge, Massachusetts: Harvard University Press.
  ISBN 0-674-95607-9
  .
• Putnam, H. (1995). Pragmatism: An Open Question. Oxford: Blackwell.
  ISBN 0-631-19343-X. Based on the Gifford Lectures that Putnam delivered at the University of St Andrews in 1990 and 1991.^[103]
• Putnam, H. (1999). The Threefold Cord: Mind, Body, and World. New York: Columbia University Press.
  OCLC 868429895
  .
• Putnam, H. (2001). Enlightenment and Pragmatism. Assen: Koninklijke Van Gorcum.
  OCLC 248668591
  .
• Putnam, H. (2002). The Collapse of the Fact/Value Dichotomy and Other Essays. Cambridge, Massachusetts: Harvard University Press.
  ISBN 0-674-01380-8
  .
• Putnam, H. (2002). Ethics Without Ontology. Cambridge, Massachusetts: Harvard University Press.
  ISBN 0-674-01851-6
  .
• Putnam, H. (2008). Jewish Philosophy as a Guide to Life: Rosenzweig, Buber, Levinas, Wittgenstein. Bloomington: Indiana University Press.
  OCLC 819172227
  .
• Putnam, H. (2012). De Caro, M.; Macarthur, D. (eds.). Philosophy in an Age of Science. Cambridge, Massachusetts: Harvard University Press.
  OCLC 913024858
  .
• Putnam, H. (2016). De Caro, Mario (ed.). Naturalism, Realism, and Normativity. Cambridge, Massachusetts: Harvard University Press.
  ISBN 978-0-674-65969-8
  .
• Putnam, H.; Putnam, R. A. (2017). Macarthur, David (ed.). Pragmatism as a Way of Life: The Lasting Legacy of William James and John Dewey. Cambridge, Massachusetts: Harvard University Press.
  ISBN 978-0-674-96750-2
  .

• Putnam, H. (1964).
  ISBN 0-521-29648-X
• OCLC 299388752
  .
• Essler, Wilhelm K.; Putnam, H.;
  OCLC 793401994
  .

• .Putnam, H. (March 1967). "The 'Innateness Hypothesis' and Explanatory Models in Linguistics". Synthese. 17 (1): 12–22.
  S2CID 17124615
  .

An exhaustive bibliography of Putnam's writings, compiled by John R. Shook, can be found in The Philosophy Of Hilary Putnam (2015).[104]^[105]

• American philosophy
• List of American philosophers