Article abstract: Putnam is probably best known for his development and defense of Turing machine functionalism, for his concept of semantic externalism and the Twin Earth thought exercise, and for internal realism.

Early Life

On July 31, 1926, Hilary W. Putnam was born in Chicago to Samuel and Riva Putnam. Samuel was a writer and a journalist and a member of the Communist Party during the Depression. Putnam’s parents lived in France until 1934 and then in Philadelphia, where Putnam was graduated from the University of Pennsylvania in 1948. He studied at Harvard for a year before eventually earning his Ph.D. from the University of California, Los Angeles, in 1951.

At the age of twenty-two, Putnam married Erna Diesendruck on November 1, 1948. They divorced in 1962, and he married Ruth Anna Hall on August 11 of that year. He became the father of four children, two daughters and two sons.

Life’s Work

Putnam began teaching philosophy as an instructor at Northwestern University in 1952. That year was followed by a stint at Princeton, where he advanced to assistant and later associate professor. He then taught, as a full professor, at the Massachusetts Institute of Technology from 1961 to 1965. Beginning in 1965, he taught philosophy at Harvard under various titles, including Walter Beverly Pearson Professor of Modern Mathematics and Mathematical Logic and Cogan University Professor. He served the Eastern Division of the American Philosophical Association as vice president for 1975-1976 and as president for 1976-1977.

According to an article that appeared in the news magazine U.S. News and World Report, Putnam supported the draft resistance during the Vietnam War and later, having become more radicalized, assumed the position of Harvard faculty sponsor of Students for a Democratic Society (SDS) and joined a Maoist group, the Progressive Labor Party. According to Putnam, this Marxist period in his life may have been a retracing of his father’s footsteps.

Putnam’s topics include a vast array of philosophical issues, from the theoretical foundations of quantum physics to the epistemology of ethics, but as indicated by the title of his Ph.D. dissertation, The Meaning of the Concept of Probability in Application to Finite Sequences, his early work focused primarily on logic and the philosophy of mathematics. A notable contribution in these fields is his work with Martin Davies and Julia Robinson. Davies and Putnam teamed to write “Reductions of Hilbert’s Tenth Problem,” and Putnam, Davies, and Robinson wrote “The Decision Problem for Exponential Diophantine Equations.”

In the late 1950’s, Putnam proposed a program in the philosophy of mind that is now widely known as functionalism. Functionalism, according to Putnam, is the view that mental states, rather than being identified as some physical state, are defined by their inputs and outputs, or causes and effects. Putnam stated that the mind may be viewed as a “probabilistic automaton” of which, in some state, the transition to other states and the display of certain behaviors can be probabilistically predicted based on a given input, or set of inputs. The Turing machine, often used by Putnam to explain and defend functionalism, is a special type of probabilistic automaton with transition probabilities 1,0. That is, the strictly binary probabilities of the Turing machine are, more than probabilistic, deterministic.

Putnam’s argument rests largely on the thesis that states such as pain are not physical-chemical states of the brain, but functional states of the entire organism. Given some typical state of the organism, pain is the state caused by a certain input, such as a pinch or a pinprick, that in turn causes other states, such as worry or apprehension, and behaviors (output) such as exclaiming, “Ouch!” What he intended to show, through functionalism, was that organisms composed of physically possible but different material could as easily exhibit mentality as do humans. From this we learn that what we really want to know about the mind is its functional organization, not the nature of its either mysterious or strictly physical substance.

About the time that Putnam became more politically radical, his philosophical views moved away from positivism and became less concerned with logic and the philosophy of mathematics. The focus of his work shifted to human experience and how human experience is affected by fields such as logic, philosophy of mathematics, epistemology, and other areas of philosophy.

Putnam often changed his mind. Early in his career, he was a strong proponent of the positivist movement, which he later abandoned and even criticized. In addition, although he defended and developed the theory of functionalism, he came to argue that functionalism fails because the intentional cannot be reduced to the computational or physical. However, Putnam basically held one position (though often revised) beginning in the late 1950’s: The main concepts of that position are “semantic externalism” and “internal realism.”

Semantic externalism, or the notion that “‘meanings’ just ain’t in the head” was first introduced, using the Twin Earth thought experiment, in Putnam’s 1975 essay, “The Meaning of ‘Meaning.’” Twin Earth is exactly like Earth in every way except one—the word “water,” though indicating the substance filling ponds, running through pipes, and drunk from glasses, does not refer to H2O, but XYZ. In spite of its distinct chemical makeup, XYZ is utterly indistinguishable from water to the layperson, and it is only with the aid of modern science that Earth and Twin Earth inhabitants are aware of the difference between the two substances.

Putnam proposed semantic externalism as a response to the popular and pervasive notion according to which knowledge of meanings is private. A feature common to all theories of meaning, from those of Greek philosopher Aristotle to those of Scottish philosopher David Hume, is that an individual in isolation can grasp any concept and that the individual’s grasp of the concept completely determines the extension of that concept. The difference between the extension of “water” on Earth and the extension of “water” on Twin Earth is intended to show that extension of terms is at least partially dependent on factors external to any individual’s mind.

An increasingly staunch critic of metaphysical realism, Putnam strove to show that the collapse of such realism does not require us to fall into relativism or postmodern skepticism. He introduced his concept of internal realism in a presidential address to the American Philosophical Association in 1976. Essentially, internal realism, or realism with a little “r,” as Putnam termed it, takes both the commonsense view of things and the scientific view of things at face value without “helping itself to a notion of the ‘thing in itself.’” In his 1987 essay “Is There Still Anything to Say About Reality and Truth?,” Putnam said that “internal realism … is just the insistence that realism is not incompatible with conceptual relativity.” That is, internal realism is not in conflict with the idea that we can, and perhaps should, use different theories about the world in different circumstances. To illustrate this idea, Putnam recalled that the typical person views a table as “solid,” or as mostly solid matter, even though physics has shown that the table is, in fact, mostly empty space.

Other consistent themes in Putnam’s work, particularly his later work, are his attack on the fact-value dichotomy and his praise of American pragmatism. Both themes are found throughout the papers in Reason, Truth, and History and Words and Life. In these works, he suggests that it is a mistaken view to claim that ethics and aesthetics do not deal in facts because they are ultimately value-based and to think that metaphysics is any less ultimately grounded in values.

These themes might both be considered a part of Putnam’s push to bring philosophy back to the people, another central theme in his later work. As the Gifford Lecturer at the University of St. Andrews during the Martinmas term of 1990, Putnam presented a series of lectures to this end that were later published as Renewing Philosophy. Philosophy was taken from the people, in his view, through its own mistaken views of its purpose and value. These views, which Putnam sometimes attributes to particular philosophers and other times simply to the discipline as a whole, grant either too much or too little importance to philosophy:

For philosophy to see itself simply as thinking about a collection of riddles seems too small an ambition, but for philosophy to have the ambition of saving the world seems too extreme. Something in between has got to be right.

Influence

Putnam’s influence on philosophy is difficult to measure because his writings span a wide breadth and contain evolving views. Nevertheless, some conclusions can be made with a fair amount of certainty.

Putnam, like many other scholars, benefited from the mass intellectual exodus of Europe resulting from Nazi occupation prior to and during World War II. A student of both Rudolf Carnap and Hans Reichenbach, Putnam frequently acknowledged Reichenbach’s influence on his work. Among the connections to his teacher is the substantial contribution to the theoretical foundations of quantum physics.

In his works, Putnam drew extensively on the influence of both philosophers Immanuel Kant and Ludwig Wittgenstein and expressed a desire to think of some of his own views as Kantian. In addition, he wrote that though Kant was wrong about quite a bit, the solution lies not in asking new or different questions but in correctly answering the questions that Kant aptly raised.

There is no denying the strong influence of pragmatism on Putnam’s work, his later work in particular. Putnam made no secret of his affinity to that school of thought and indeed seemed to view himself somewhat as a contemporary pragmatist. In the preface to Words and Life, he suggested that he should have called internal realism pragmatic realism. Also, in the preface to Realism with a Human Face, he allied his views with “the generous and open-minded attitude that William James called ‘pragmatism’” as opposed to the “science worship” of the positivists.

Putnam’s early work is likely to have a long-lasting impact on logic and the philosophy of mathematics. Likewise, his work on functionalism, though ultimately rejected by Putnam himself, was quite influential in the philosophy of mind. Though it is yet unclear whether Putnam’s later work will accomplish his goal of renewing philosophy, it is likely that it will have significant implications for the field and that, if nothing else, Putnam’s thought will play a part in rejuvenating the pragmatist movement in philosophy.

Additional Reading

Boolos, George, ed. Meaning and Method: Essays in Honor of Hilary Putnam. Cambridge, England: Cambridge University Press, 1990. Boolos presents a series of papers by several of Hilary Putnam’s colleagues and former students. The papers cover a wide variety of philosophical subjects, reflecting Putnam’s own interests and his pervasive influence on contemporary thought.

Clark, Peter, and Bob Hale, eds. Reading Putnam. Cambridge, Mass.: Blackwell, 1994. Papers from nine philosophers presented at an international conference on Putnam’s philosophy at the University of St. Andrews in 1990 are collected in this volume. They represent a broad range of issues to which Putnam has contributed significantly. Two essays in particular, Simon Blackburn’s “Enchanting Views” and Michael Dummet’s “Wittgenstein on Necessity: Some Reflections,” focus on Putnam’s internal realism. Blackburn tells us what internal realism is not.

Goldberg, Sanford, and Andrew Pessin, eds. The Twin Earth Chronicles: Twenty Years of Reflection on Hilary Putnam’s “The Meaning of ‘Meaning.’” Armonk, N.Y.: M. E. Sharpe, 1996. This is a good initiation to one of Putnam’s major ideas, “semantic externalism.” This collection begins with an introduction, followed by “The Meaning of ‘Meaning,’” Putnam’s article challenging traditional views of the philosophies of language and mind. The remainder of the work is dedicated to arguably the best of many responses the article generated.

Harman, Gilbert. “Metaphysical Realism and Moral Relativism: Reflections on Hilary Putnam’s Reason, Truth, and History.” The Journal of Philosophy 79, no. 10 (October, 1982): 568-575. This is a useful critique of internal realism, based on a defense of the fact-value distinction. This is one of two papers that generated Putnam’s own “A Defense of Internal Realism” in Realism with a Human Face. The other, also in this issue, along with Putnam’s brief responding comments, is Hartry Field’s “Realism and Relativism” on pages 553-567.