The American philosopher John Searle, who has died aged 93, first made his name in philosophy of language, then in philosophy of mind, and finally in “philosophy of society”, a new field of study that he helped to establish. He aimed to produce a unified theory of all three.

His overall question, posed in Making the Social World (2010), was: “How is it possible in a universe consisting entirely of physical particles in fields of force that there can be such things as consciousness, intentionality [the “aboutness” of thinking], free will, language, society, ethics, aesthetics and political reality.”

Searle’s famous Chinese Room thought experiment was designed to rebut the fashionable view that human and animal mental states are tantamount to computer programmes. It demonstrated that, in themselves and unless interpreted by outside agents, a computer’s inputs and outputs would just be arbitrary symbols. Yet Searle did not regard mental states as non-physical. With all their “aboutness” and subjectivity, he argued, they are as much biological phenomena as digestion and blood flow are.

He fiercely combated French-derived views that reality is a social construction, but argued that the “social facts” we have created, thanks to language, are as obdurately actual in our lives as “brute facts”. Notoriously, he had long-running, rancorous disputes with both the physicalist Daniel Dennett and the deconstructionist Jacques Derrida.

Apart from holding visiting professorships worldwide, Searle spent his entire academic career at the University of California, Berkeley, where he was Slusser professor of mind and language for almost 60 years.

Aged 27, he had been recommended for a lectureship there by JL Austin, a celebrated philosopher at Oxford University, where Searle gained a degree in philosophy, politics and economics in 1955, and a doctorate (1959). Having studied for two years at his local university, Wisconsin-Madison, he had won a Rhodes scholarship to Oxford – unaware, he later insisted, that philosophy at the university was going through “a golden age”.

Austin in Oxford, and Wittgenstein in Cambridge, were placing language at the forefront of philosophy by showing that it frames our world, and that, rather than being primarily descriptive, it is an extension of our other activities – of commanding, promising, joking, praying, exclaiming, hypothesising, and so on. Initially bored by Austin’s lectures, Searle became fascinated by his notion of language as performative – that it is often used not to report on but to change reality, bringing new facts into being (“Get out!”, “I pronounce you man and wife”, “I do”, “I promise to pay you £5”); that we often make a statement in order to convey something completely different to what it literally means (for instance, a veiled threat, an implied warning), or even the very opposite, such as a sarcastic “how clever!”.

Although Searle’s cowboy-style bluffness was at odds with the patrician style of the pedantic, self-contained Austin, they were united in no-nonsense realism. It was in Austin’s office that Searle met Dagmar Carboch, a Czech research student, whom he married in 1958, and who later became an attorney.

Using Austin’s approach, Searle’s 1964 paper How to Derive “Ought” from “Is” purported to dissolve the supposedly unbridgeable gap (in moral philosophy) between factual statements and moral prescriptions. Some rules, argued Searle, do not just regulate particular actions “from outside” – they constitute the very possibility for such actions to occur.

It is a fact that Jones has uttered the words “I promise to pay you, Smith, £5”, and thereby made a promise. And a promise “is, by definition, an act of placing oneself under an obligation”, and of predicating a future event that the person promised is entitled to expect. The storm of disagreement that greeted Searle’s paper put him on the philosophical map; still more did his first book, Speech Acts (1969), which developed and systematised Austin’s ideas on the varieties of language use.

For more than a century, philosophers of mind have been seeking to produce some homogeneously physical account of the world, but so far have failed satisfactorily to accommodate certain features of the mind – qualia (the “what-it-is-like” subjective qualities of consciousness) and intentionality (a technical term for the way thoughts are about external things).

A purported solution, popular since the 1960s, is to analyse feelings and sensations as elements in a causal network of bodily stimulus and response, and to equate the mind with processing software implemented by the hardware of the brain. Thus, once a computer’s outputs are sufficiently complex to be indistinguishable from those of a human being, it will pass the famous Turing test – that is, will count as thinking.

In 1980, while flying to a conference in Texas, Searle devised the Chinese Room thought experiment, discussion of which replaced the papers scheduled to be given. It asks us to imagine a man who, through a slot in a sealed-off room, receives slips of paper covered with what seem to him squiggles, but are in fact Chinese characters. Guided by a manual, he rewrites these in different combinations, and posts the results through another slot. Chinese-speaking recipients outside read them as answers to the questions originally posed, for “the outputs are indistinguishable from those of a native Chinese speaker”.

Yet surely understanding a language is more than “manipulating formal symbols”, which is all the man does? His outputs, like those of a computer that passes the Turing test, are inescapably “observer-relative” – in order to constitute information, they need to be interpreted by someone who understands them; they do not understand themselves. Without humans to create, and then adjudicate it, how could a processing system be judged as convincingly human?

Symbols in language or processing, said Searle, have “derived intentionality” – have meaning thanks to certain correspondences first set up, then recognised, by their users. Mental states (in humans and animals), however, have “intrinsic intentionality” – they are “caused by neurophysiological processes in the brain,” he wrote in The Rediscovery of the Mind (1992), “and are themselves higher-level features of the brain”.

And, as he observed in Intentionality (1983): “No one ever considered his own terrible pain or his deepest worry and concluded that … they could be entirely defined in terms of their causes and effects.” That mental states are subjective, intentional and qualitative is, he said, “an objective fact about the world”.

Searle accused physicalists of simply repeating the mistake of their dualist opponents – refusing to admit the possibility that mental processes can be “part of our biology”. He had, he asserted, found “an alternative between the Scylla of dualism and the Charybdis of materialism” in his position of “biological naturalism”. But philosophers of both persuasions criticised it for being either inadvertently dualist, or for begging the question. Whether, and how, mental states can be neurophysiological was precisely what he needed to prove.

In their long-running dispute, Searle persuaded Derrida to at least modify the claim that “there is nothing outside the text”. He himself, in The Construction of Social Reality (1995) and Making the Social World, extended the remit of realism. Money, property, frontiers, elections, for instance, were not pre-existing physical facts, but, he argued, are “facts that have been brought into existence”. They form an objective social reality, not due to individual edict but to the “collective intentionality” enabled by language (and to what Searle called “the Background” of our neurophysiological capacities).

Searle was born in Denver, Colorado. His mother, Hester (nee Beck), was a doctor, who died when he was 13. His father, George, was a business executive in an electrical engineering firm. The family moved to New York, then Shorewood, Wisconsin, where Searle attended Shorewood high school.

At the University of Wisconsin, he became secretary of the Students Against Joseph McCarthy group. He was the first tenured professor at Berkeley to join the students in the 1964-65 free speech movement, but in 1969 he sided with the university against the students.

Beer often featured in his down-to-earth philosophical examples, but he came to be a connoisseur of wine and owned a vineyard in Napa Valley. Yet his cowboy style and rough-edged growl persisted. Sometimes described as a “stand-up philosopher”, he was a funny, eloquent speaker and won Berkeley’s distinguished teaching award in 1999.

However, in 2017 a lawsuit alleging sexual harassment was brought against him, and after the university found that he had violated their policies, in 2019 he was stripped of his emeritus status.

Searle cared for his wife in the years leading to her death in 2017. They had two sons, Thomas and Mark.

• John Rogers Searle, philosopher, born 31 July 1932; died 17 September 2025