Hilary Putnam

Quick Facts

• Full name: Hilary Whitehall Putnam
• Lived: 1926-2016
• Born: Chicago, Illinois; died in Arlington, Massachusetts
• Main fields: philosophy of language, mind, science, mathematics, logic, ethics
• Main traditions: Analytic Philosophy, philosophy of mind, later Pragmatism
• Teaching posts: Northwestern, Princeton, MIT, Harvard
• Best-known ideas: semantic externalism, Twin Earth, functionalism, multiple realizability, internal realism, brain in a vat, fact-value entanglement

The Big Question

How can human thought be objective if our words, theories, values, and practices are always part of the way we understand the world?

Putnam rejected two easy answers. Truth is not just whatever our culture says it is. But philosophers also cannot describe reality from nowhere, outside every human concept. The world pushes back on us, but we meet it through language, science, social practices, and value-laden inquiry.

In One Minute

Hilary Putnam was one of the most influential American philosophers of the late twentieth century. He worked across mind, language, science, truth, mathematics, ethics, and religion. He was also famous for changing his mind in public.

His most famous slogan is that meaning is not just in the head. What a word means depends partly on the world it points to and on the community that uses it. His Twin Earth example made that point famous. He also helped create functionalism, attacked simple pictures of realism, and later defended a pragmatist view in which fact, value, and inquiry are intertwined.

What They Taught

Putnam taught that thought is not sealed inside the skull. We think with brains, but meanings and beliefs also depend on things around us, the language community we belong to, and the practices that let us test and correct ourselves.

This is clearest in his philosophy of language. Older theories often treated meaning as something inside the speaker: a mental image, a definition, a list of descriptions, or a private intention. Putnam argued that "water" is not fixed only by the picture in my head. It also depends on the actual substance people in my world call water.

He made the point with Twin Earth. Imagine a planet just like Earth in ordinary life. People there drink a clear liquid, swim in it, and call it "water." But its chemical structure is not H2O. It is XYZ. Before modern chemistry, an Earth speaker and a Twin Earth speaker could have the same mental picture and everyday beliefs. Still, the Earth word "water" refers to H2O, while the Twin Earth word refers to XYZ. This is semantic externalism: meaning depends partly on factors outside the individual mind.

Putnam also argued that language has a division of linguistic labor. Most people can use words like "elm," "beech," "arthritis," or "gold" without being experts. A community lets ordinary speakers rely on specialists. I can talk about gold even if a chemist knows far more than I do about what makes gold gold.

In philosophy of mind, Putnam helped make functionalism a major view. Functionalism says a mental state is defined by the role it plays: what causes it, how it connects with other states, and what behavior it tends to produce. Pain is not one exact brain material. It is the state normally caused by damage, tied to distress, and likely to produce avoidance or complaint.

This led to multiple realizability. The same mental kind might be realized in different physical materials. A human, an alien, and a future machine could all feel pain or solve a problem without sharing one identical brain state. This challenged mind-brain identity theory, which tried to identify each mental state type with one brain state type.

Putnam's view of realism changed many times. Early on, he defended scientific realism: successful science is not just useful prediction, but usually gets something right about the world. Later he attacked metaphysical realism: the view that there is one fully fixed description of the world, independent of all human concepts, and that truth is a match with that ready-made world.

His alternative was internal realism, later softened into pragmatic realism or commonsense realism. Reality is not invented by us. We can be wrong, and experiments can fail. But truth and reference are understood from within human practices of inquiry, not from a God's-eye view outside all human life.

Putnam used the brain-in-a-vat thought experiment to connect meaning with skepticism. Suppose someone has always been a brain in a vat, fed artificial experiences by a computer. Putnam argued that such a person could not use "brain" and "vat" to refer to real brains and vats outside the system. So "I am a brain in a vat" cannot express the skeptical possibility in the intended way.

Late in life, Putnam turned toward ethics, Jewish thought, and pragmatism. He denied a clean fact-value split. A fact says how things are. A value judges what is good, bad, reasonable, cruel, fair, or worth doing. Calling a policy "cruel" describes what it does and evaluates it. Even science uses values such as simplicity, coherence, accuracy, and explanatory power.

Key Ideas With Examples

• Semantic externalism: meanings are not fixed only inside one person's mind. If two people picture "water" the same way, but one is connected to H2O and the other to XYZ, their words can refer to different things.
• Twin Earth: a duplicate-Earth thought experiment where the local "water" acts like water but has a different chemical structure. It shows why meaning depends on the world, not just on descriptions in the head.
• Division of linguistic labor: a community shares the work of keeping words tied to things. You can use "elm" correctly even if a botanist has to identify the tree.
• Functionalism: a mental state is identified by what it does. A thermostat, a human, and a robot could all have a state that plays the role of "detecting too much heat," even if the physical material is different.
• Multiple realizability: one kind of state can be realized in many physical ways. Pain in humans may involve one nervous system pattern; pain in another creature might work differently while still playing the pain role.
• Internal realism: truth is objective, but we understand and test truth from within human concepts and inquiry. A map can be more or less accurate, but there is no map drawn from no point of view at all.
• Model-theoretic argument: a technical argument that formal relations alone do not fix exactly what our words refer to. If a theory is just a structure, more than one interpretation may fit it.
• Brain in a vat: a skeptical scenario where a brain receives fake experiences. Putnam's reply is that a lifelong envatted brain would not have words connected to real brains and vats.
• Fact-value entanglement: description and evaluation often come together. "This was a cruel punishment" says something about what happened and judges it at the same time.

Major Works

• "The Nature of Mental States" (1967): Putnam's classic statement of functionalism and multiple realizability. It argues that mental states should not be reduced to one physical brain-state type.
• "The Meaning of 'Meaning'" (1975): the source of Twin Earth. It attacks private, description-based accounts of meaning and explains the social division of linguistic labor.
• Mind, Language and Reality (1975): a major collection on mind, language, science, and reference. It shows his early analytic style at full strength.
• Mathematics, Matter and Method (1975): essays on logic, mathematics, and science, including scientific realism, quantum logic, and theory choice.
• Reason, Truth and History (1981): Putnam's best-known book on realism, truth, and skepticism. It develops internal realism and presents the brain-in-a-vat argument.
• Representation and Reality (1988): Putnam's self-critique of earlier computational and functionalist assumptions. It argues against treating meanings as fixed inner symbols alone.
• Realism with a Human Face (1990): essays on realism, objectivity, and relativism. Putnam keeps realism but rejects the dream of a God's-eye description.
• The Collapse of the Fact/Value Dichotomy (2002): Putnam's mature argument that facts and values are not cleanly separable.

Why It Matters

Putnam matters because many later debates start from his examples. Twin Earth is still a standard way to introduce meaning and reference. Multiple realizability is still a major objection to reducing mind to brain-state types. The brain-in-a-vat argument remains a famous attempt to answer radical skepticism with philosophy of language.

He also refused two bad extremes. Truth is not whatever people agree to say. But objectivity does not require a God's-eye view. That middle path shaped late analytic philosophy, pragmatism, and debates about realism.

Putnam's career is also a model of public self-correction. He changed his views on functionalism, realism, and pragmatism when he thought his own arguments had gone too far. That made his work difficult to summarize, but unusually honest.

Proponents, Critics, and Opponents

Putnam was shaped by W. V. O. Quine's naturalism and holism, but thought Quine made meaning and value too thin. He inherited formal ambitions from Rudolf Carnap, while rejecting a strict split between facts and framework choices.

Putnam and Saul Kripke helped move philosophy of language away from the idea that reference is fixed by private descriptions. Putnam's Twin Earth argument became one of the starting points for externalist theories of meaning and mind.

Donald Davidson shared some anti-skeptical concerns, but rejected talk of different conceptual schemes more sharply than Putnam did. John Searle criticized computational pictures of mind from another direction. Richard Rorty shared Putnam's pragmatist interests, but Putnam thought Rorty moved too close to anti-realism.

Putnam's later work revived themes from William James and John Dewey: inquiry happens in life, truth matters because practices can be corrected, and values are part of intelligent inquiry.

Related Pages

• Analytic Philosophy
• Pragmatism
• W. V. O. Quine
• Rudolf Carnap
• Saul Kripke
• Donald Davidson
• John Searle
• Richard Rorty
• William James
• John Dewey