Timeline of type A physicalism

This is a timeline of Type-A physicalism, tracing the rise of naturalistic, anti-dualist accounts of consciousness from ancient atomism and Cartesian dualism through behaviorism, identity theory, and functionalism, to Dennett's heterophenomenology, Chalmers's explanatory-gap taxonomy, and Frankish's illusionism. It follows this lineage into 2020s research linking predictive processing, global workspace theory, and AI consciousness debates, situating Type-A approaches within a still-pluralistic field. Type-A physicalism is the view that there is no genuine explanatory gap between physical facts and consciousness — denying that there's anything left to explain once all the physical and functional facts are in, including denying or explaining away the intuition that subjective experience poses a special further mystery.

Sample questions

The following are some interesting questions that can be answered by reading this timeline:

• What are some of the foundational philosophical works that established the dualist framework physicalists would spend centuries responding to, and the early materialist precursors to modern physicalism?
  • Sort the full timeline by "Event type" and look for the group of rows with value "Philosophical work" or "Philosophical doctrine".
  • You will see a small number of foundational texts spanning Democritus's atomism and Aristotle's hylomorphism to Descartes's substance dualism, Hobbes's materialism, and Spinoza's monism, illustrating how the basic terms of the mind-body debate were set well before "physicalism" existed as a labeled position.
• What are the landmark journal articles and books that mark the rise and development of identity theory, functionalism, eliminative materialism, and illusionism over the past three centuries?
  • Sort the full timeline by "Event type" and look for the group of rows with value "Publication".
  • You will see the large majority of rows in this timeline, since most of the history of Type-A physicalism unfolds through journal articles and books rather than institutional events — from La Mettrie and Priestley through Ryle's Concept of Mind, Putnam's functionalism papers, the Churchlands' eliminativism, Dennett's long sequence of works, and Frankish's and Kammerer's illusionist papers.
• What institutional milestones gave naturalistic philosophy of mind and cognitive science their organizational backbone?
  • Sort the full timeline by "Event type" and look for the group of rows with value "Journal founded", "Society founded", or "School founded".
  • You will see the founding of the journal Cognitive Science (1977), the Cognitive Science Society (1979), and the founding of behaviorism as a school of psychology by Watson (1913), each giving a research program institutional identity that outlasted any single publication.
• What conferences and manifestos brought scattered naturalistic thinkers together into organized movements?
  • Sort the full timeline by "Event type" and look for the group of rows with value "Conference" or "Manifesto".
  • You will see the Vienna Circle's 1929 manifesto, the 1935 First International Congress for the Unity of Science, and Frankish's 2014 "consciousness cruise" where the term "illusionism" was first proposed in public debate — each a moment where individual ideas became a collective program.
• What are the major experimental and scientific findings that have been invoked as evidence for or against Type-A physicalism?
  • Sort the full timeline by "Event type" and look for the group of rows with value "Scientific paper", "Scientific discovery", or "Scientific development".
  • You will see neuroscientific milestones from Hitzig and Fritsch's 1870 cortical stimulation experiments through McCulloch and Pitts's artificial neuron model and Minsky's SNARC machine, tracing the physical and computational evidence base that later philosophical arguments draw on.
• What are the broader intellectual movements and ongoing research trends, as opposed to single landmark publications, that this timeline tracks?
  • Sort the full timeline by "Event type" and look for the group of rows with value "Intellectual movement", "Intellectual trend", or "Research trend".
  • You will see composite rows summarizing logical positivism's behavioral turn (1930s–1950s), predictive coding's rise in cognitive neuroscience (2012), and the 2020s convergence of computational theories of consciousness with debates about AI sentience — rows that capture a trend rather than a single dated event.
• When and how did the central organizing concepts of this timeline — the "hard problem," the Type-A/B/C taxonomy, and "illusionism" — get named?
  • Sort the full timeline by "Event type" and look for the group of rows with value "Concept popularized" or "Classification introduced".
  • You will see Chalmers popularizing the "hard problem" in 1996 and formally introducing the Type-A/B/C/D/E/F taxonomy in 2002 — giving this entire timeline, and the broader field, its organizing vocabulary.
• Other events are described under the following types: "Philosophical argument", "Edited volume", and "Theoretical development".

Big picture

Time period (approximately)	Development summary	More details
c. 400 BCE – 1814	Materialist accounts of mind emerge as a recurring minority position challenging dualist and idealist frameworks	Ancient atomists like Democritus ground mental phenomena in the motion of material atoms, while Aristotle's hylomorphism offers a competing naturalistic but non-reductive picture of soul. Descartes's substance dualism (1637–1641) becomes the framework materialists react against for the next two centuries: Hobbes treats humans as "matter in motion," La Mettrie extends Cartesian mechanism explicitly to human beings, and Priestley and Cabanis ground mind in Newtonian physics and physiology. By the early 19th century, Laplace's strict physical determinism extends mechanistic thinking about nature into a worldview that would later shape conceptions of mind and behavior.
1855–1936	Materialism gains experimental and institutional backing even as rival idealist and naturalist accounts persist, while psychology becomes a laboratory science	Büchner's Kraft und Stoff (1855) popularizes scientific materialism across Europe, while Hitzig and Fritsch's cortical stimulation experiments (1870) give materialism its first genuine experimental ally. Darwin and Huxley extend evolutionary and mechanistic thinking to emotion and consciousness itself, even as Clifford's competing "mind-stuff" theory shows that scientific naturalism of the era did not converge on a single answer. James and Ebbinghaus establish psychology as an experimental science, and Watson's behaviorist manifesto (1913) pushes this empiricism to the point of rejecting introspection outright. Meanwhile, the Vienna Circle (1929) and Turing's universal computing machine (1936) supply, respectively, the philosophical and technical seeds from which identity theory and computationalism will later grow.
1949–1989	Mind is identified with brain processes, then reframed functionally, while a more radical wing argues that everyday mental vocabulary itself may need to be abandoned	Ryle's attack on Cartesian dualism (1949) sets the stage for Place's and Smart's "Australian materialism" and Feigl's parallel "Austrian" identity theory, all identifying mental states directly with brain processes. Putnam, Lewis, and Armstrong then develop functionalism as a more flexible alternative compatible with multiple physical realizations of the same mental state, while Nagel's and Kripke's arguments expose limits the program has had to answer ever since. In parallel, Feyerabend, Rorty, and the Churchlands argue that folk-psychological concepts like belief and desire may be scientifically inadequate and eventually replaceable by neuroscience, a position Fodor's computational theory of mind and the newly founded field of cognitive science (1977–1979) approach from the opposite direction — building up, rather than tearing down, a scientific vocabulary for mind.
1978–2009	Dennett develops a comprehensive naturalistic theory of consciousness, Chalmers names and formalizes the explanatory-gap debate, and representationalists attempt reductive accounts of phenomenal experience	From Brainstorms (1978) through Consciousness Explained (1991) and beyond, Dennett rejects qualia and the "Cartesian Theater" in favor of the Multiple Drafts Model and heterophenomenology, a method for treating first-person reports as data rather than infallible testimony. Chalmers's "hard problem" (1996) and his Type-A/B/C/D/E/F taxonomy (2002) give the entire field — and this timeline — its organizing vocabulary, against which Tye, Dretske, Metzinger, and Papineau develop competing representationalist, self-model, and Type-B physicalist responses.
1983–2021	A growing number of philosophers argue that phenomenal consciousness itself, not merely our theories of it, is an illusion	Rey, Schwitzgebel, and Kammerer build the empirical and philosophical case that introspection systematically misrepresents mental states, well before the position has a settled name. Frankish coins "illusionism" at a 2014 conference and formally in 2016, and Dennett, Blackmore, Humphrey, and other prominent philosophers rally to the position the same year, with Frankish, Kammerer, and Dennett continuing to formalize and defend it into the early 2020s.
2010–2025	Neuroscientific and computational theories of consciousness proliferate and increasingly intersect with questions about machine consciousness, even as the field remains genuinely pluralistic	Predictive processing, global workspace theory, and Graziano's attention schema theory converge in explicit reconciliation attempts by the late 2010s, aiming to show that rival research programs are complementary rather than competing. The release of capable conversational AI systems — the LaMDA controversy of 2022 and the large language models that followed — pushes illusionist and Type-A-style arguments explicitly into the domain of artificial intelligence, with Chalmers and later Bengio asking whether such systems could be, or merely appear to be, conscious. Surveys cataloguing over 200 rival theories and adversarial empirical tests comparing leading frameworks head-to-head confirm that, even as Type-A and illusionist approaches gain ground, the science of consciousness remains a contested, pluralistic field.

Full timeline

Inclusion criteria

We include:

• Direct statements of Type-A physicalism, eliminativism, or illusionism, regardless of publication venue, since these positions are the timeline's core subject.
• Major historical materialist and naturalist precursors to Type-A physicalism, even predating the label itself, where a publication or event established or significantly extended the materialist lineage the modern position inherits.
• Contrasting and rival positions — dualism, idealist monism, neutral monism, Type-B materialism, panpsychism, and emergentism — where they directly shaped, were targeted by, or are explicitly engaged with by later Type-A physicalists or illusionists covered elsewhere in the timeline.
• Canonical anti-physicalist arguments that later Type-A physicalists and illusionists have had to directly answer, even though the arguments themselves are not physicalist.
• Institutional milestones — founding of journals, societies, conferences, and manifestos — that materially advanced the physicalist or naturalist research program as a collective enterprise, not just an individual's views.
• Empirical and neuroscientific findings explicitly invoked, by philosophers or by the original researchers, as bearing on Type-A physicalism, illusionism, or a named rival theory of consciousness.
• Multiple papers by the same prolific contemporary author where each marks a genuinely distinct development of their position — a new argument, a new target, or a reply within a documented exchange.

We exclude:

• General neuroscience or AI research on consciousness that does not explicitly engage with Type-A physicalism, illusionism, or one of the named rival theories already covered in the timeline.
• Minor or incremental restatements of a position an author has already stated elsewhere in the timeline, where the later piece adds no new argument, target, or development.
• Conferences, workshops, or institutional events tangential to philosophy of mind that did not materially advance a naturalistic or physicalist research program specifically.
• Biographical or career details of philosophers covered in the timeline that are not directly tied to the development or defense of a position relevant to Type-A physicalism.
• Broad surveys or popular-science treatments of consciousness that do not stake out or engage with a position on the explanatory gap, unless they are themselves widely cited as benchmarks of the field's state (e.g. comprehensive taxonomies of competing theories).

Year	Event type	Details
c. 400 BCE	Philosophical doctrine	Pre-Socratic philosopher Democritus, building on Leucippus, develops an atomistic theory of nature in which mental phenomena are ultimately explained by the motion of material atoms — describing the soul as composed of especially fine, smooth, spherical atoms that animate the body and dissolve at death, with sensation and thought arising from atoms striking the sense organs and propagating motion to a "center of consciousness." The view is later dismissed by Aristotle but would be revived nearly two millennia later by Enlightenment materialists, making Democritus the earliest identifiable ancestor of the physicalist tradition this timeline traces.
c. 350 BCE	Philosophical work	Ancient Greek philosopher Aristotle's De Anima presents a hylomorphic, naturalistic investigation of the soul — defining soul as the form (organizing principle) of a living body rather than a separable substance, and treating most psychological capacities as inseparable from the body — influencing later debates about mind and matter, though Aristotle leaves the status of nous (intellect) as a possible partial exception. Unlike the atomist account of mind as literally composed of matter, Aristotle's hylomorphism treats mind as a pattern or function of matter — a distinction that anticipates the modern split between reductive (Type-A) physicalism and functionalism.
1637–1641	Philosophical work	French philosopher and mathematician René Descartes publishes Discourse on the Method (1637) and Meditations on First Philosophy (1641), formulating substance dualism and establishing the distinction between mind and body that later physicalists seek to resolve — the dualist picture against which nearly every other row in this timeline defines itself.
1651	Philosophical work	English philosopher Thomas Hobbes publishes Leviathan, defending a mechanistic and materialist conception of human thought — presenting humans as "matter in motion" and explaining sensation, imagination, and reasoning as chains of internal motions caused by external objects acting on the sense organs, without recourse to an incorporeal soul. Written within fourteen years of Descartes's Meditations, it stands as the first major materialist rebuttal to Cartesian dualism.
1677	Philosophical work	Dutch philosopher Baruch Spinoza's Ethics (Spinoza) is published posthumously, proposing a monist metaphysics in which thought and extension (mind and body) are attributes of a single infinite substance rather than distinct substances, offering an early alternative to Cartesian dualism that — unlike Hobbes's reductive materialism — treats mind and matter as equally fundamental rather than reducing one to the other.
1689	Publication	English philosopher John Locke publishes An Essay Concerning Human Understanding (first appearing in late 1689, though title-paged 1690), promoting an empiricist approach to the study of mind — rejecting innate ideas and arguing that the mind at birth is a "tabula rasa" furnished entirely through sensation and reflection, laying foundational groundwork for the empiricist tradition later drawn on by behaviorists and other naturalistic approaches to mentality.
1745	Publication	French physician and philosopher Julien Offray de La Mettrie publishes Histoire naturelle de l'âme ("Natural History of the Soul"), his first philosophical work, arguing that mental phenomena can be explained entirely through bodily processes — drawing on anatomy, physiology, and psychology to demonstrate the effects of the body on the soul, treating what had traditionally been called the soul as merely an epiphenomenon of bodily organs. The outcry it provoked forced La Mettrie's departure from Paris, foreshadowing the controversy his later, more famous works would attract.
1748	Publication	French physician and philosopher Julien Offray de La Mettrie publishes L'Homme Machine ("Man a Machine"), an early materialist account of mind that extends Descartes' view of animals as automatons to human beings, denying dualism and the existence of an immaterial soul — his most notorious and influential work, going further than his 1745 Histoire naturelle de l'âme by extending materialism explicitly to humans rather than treating it as a general thesis about body-soul interaction.
1750	Publication	French physician and philosopher Julien Offray de La Mettrie publishes Système d'Épicure ("The System of Epicurus"), further developing his materialist philosophy of mind by situating it within the ancient atomist tradition of Epicurus and Lucretius — explicitly tracing his own materialism back to the same atomist lineage as Democritus, the earliest row in this timeline — and distinctively arguing that matter is not merely the substrate of thought but inherently possesses some capacity for sensation.
1777	Publication	English theologian and natural philosopher Joseph Priestley publishes Disquisitions Relating to Matter and Spirit (printed for J. Johnson), defending a materialist account of mind against dualist theories — arguing, on Newtonian scientific grounds, that the "hypothesis" of an immaterial soul should be rejected, that a dynamic theory of matter undermines the active/passive dichotomy assumed by dualists, and that interaction between matter and spirit is impossible. Unlike La Mettrie's French Enlightenment materialism, Priestley's version is explicitly compatible with (and intended to support) Christian theology, showing materialism's reach across otherwise opposed intellectual traditions of the same century.
1802	Publication	French physician and philosopher Pierre Jean Georges Cabanis publishes Rapports du physique et du moral de l'homme (assembling memoirs first read before the Institut National beginning in 1796), arguing that thought is produced by the brain in a manner analogous to other physiological functions — declaring that "the brain digests impressions, so to speak; it organically secretes thought" — and that intellectual and moral life, being united with organic life, cannot be studied in isolation from physiology. Often credited as a founder of modern psychophysiology, Cabanis extends Enlightenment materialism (La Mettrie, Priestley) from a general philosophical thesis into the basis for a proposed medical science of mind.
1814	Publication	French mathematician and astronomer Pierre-Simon Laplace publishes Essai philosophique sur les probabilités, articulating his celebrated statement of strict physical determinism (later dubbed "Laplace's demon") — imagining an intellect that, given complete knowledge of nature's forces and the positions of all objects, could derive both the entire past and the entire future with certainty. Though Laplace was a mathematician rather than a philosopher of mind, this deterministic, mechanistic picture of nature exerted lasting influence on mechanistic conceptions of mind and human behavior throughout the nineteenth century, feeding directly into the scientific materialism of Büchner and others later in this timeline.
1855	Publication	German physician and philosopher Ludwig Büchner publishes Kraft und Stoff ("Force and Matter"), one of the most influential nineteenth-century defenses of scientific materialism — arguing that thought is as much an emanation of the brain as bile is an emanation of the liver, and that mind and spirit are products of an animal organism in the same way that motion is a product of a steam engine; the book's uncompromising materialism forced Büchner to resign his lectureship in medicine at the University of Tübingen, illustrating the social cost of openly defending physicalist views about mind even a century after La Mettrie faced similar backlash.
1866	Publication	German philosopher Friedrich Albert Lange publishes Geschichte des Materialismus und Kritik seiner Bedeutung in der Gegenwart ("History of Materialism and Critique of its Present Importance"), documenting the materialist tradition in philosophy and science — including the very figures covered earlier in this timeline, from Democritus through Büchner — in unprecedented depth, while ultimately refuting it from a Neo-Kantian standpoint: materialism, Lange argues, cannot know "things-in-themselves" and so has no stronger claim to ultimate metaphysical truth than any other system. The book nonetheless became the standard scholarly introduction to the history of materialism well into the twentieth century, shaping how later generations of philosophers (including the logical positivists) understood the tradition they were extending.
1870	Scientific paper	German physiologists Eduard Hitzig and Gustav Fritsch perform experiments on dogs demonstrating that electrical stimulation of specific parts of the cerebral cortex produces movement, overturning the long-standing belief — following the antiphrenological work of Pierre Flourens — that the cerebral cortex could not be electrically excited. This is the first solid experimental evidence for cortical involvement in motor function and the localization of mental/behavioral functions in specific brain regions, providing philosophical materialism with its first genuine experimental ally rather than purely speculative support.
1872	Publication	English naturalist Charles Darwin publishes The Expression of the Emotions in Man and Animals, encouraging evolutionary explanations of mental phenomena by extending his theory of natural selection from anatomy to emotional expression — arguing that facial and bodily expressions of emotion are continuous between humans and animals, and so are themselves products of evolution rather than divinely instituted or uniquely human. This is the founding text of evolutionary psychology and the direct ancestor of Dennett's much later (1995) argument that minds themselves are evolutionary products.
1874	Publication	English biologist Thomas Henry Huxley publishes "On the Hypothesis that Animals are Automata, and its History" in the Fortnightly Review (simultaneously in Nature), defending epiphenomenalism — the view that animals and humans are "conscious automata" whose mental life is real but causally inert, with behavior determined entirely by physical mechanisms regardless of conscious experience. The paper occasioned hundreds of discussions continuing into the 1890s and was admired by Clifford, whose competing "mind-stuff" theory appears in the next row.
1878	Publication	English mathematician and philosopher William Kingdon Clifford publishes "On the Nature of Things-in-Themselves" in Mind, developing his "mind-stuff" theory — a form of idealist monism, not materialism, in which mind is the more fundamental reality and matter is its phenomenal appearance. Though raised within the broader scientific naturalist milieu of the period (the same milieu that produced Huxley's epiphenomenalism just four years earlier), the theory anticipates panpsychism rather than physicalism, illustrating that scientific naturalism in this era did not converge on a single position about mind's place in nature.
1884	Publication	American philosopher and psychologist William James publishes "What is an Emotion?" in Mind, proposing what becomes known as the James–Lange theory of emotion (after Danish physician Carl Lange's independent 1885 formulation) — reversing the common-sense view that emotions cause bodily changes by arguing instead that bodily disturbances occur immediately upon perceiving an exciting fact, and that the feeling of these disturbances constitutes the emotion itself. James restates and develops this same theory at greater length in The Principles of Psychology six years later, the next James row in this timeline.
1885	Scientific discovery	German psychologist Hermann Ebbinghaus publishes Über das Gedächtnis ("On Memory"), pioneering experimental memory research, helping establish psychology as an empirical science — using himself as the sole experimental subject, memorizing thousands of meaningless syllables to isolate the raw mechanics of learning and forgetting independently of prior knowledge, and discovering the "forgetting curve." This methodological breakthrough — treating mental life as something to be measured in a controlled laboratory setting — directly anticipates the experimental program James lays out at book length the following year and that Watson's behaviorist manifesto would later push to its logical extreme.
1890	Publication	American philosopher and psychologist William James publishes The Principles of Psychology (Henry Holt and Company), helping establish psychology as a natural science by integrating it with physiology and biology rather than treating mind as a detached, self-sufficient soul — introducing influential concepts including the "stream of consciousness" and a functionalist view of thought and knowledge as tools for survival. James's "functional point of view" here anticipates, by some seven decades, the technical philosophical sense of "functionalism" that Putnam and Lewis would develop later in this timeline.
1900	Publication	British philosopher and logician Bertrand Russell publishes A Critical Exposition of the Philosophy of Leibniz (based on his 1899 Cambridge lectures), part of the founding wave — alongside G. E. Moore — of British analytic philosophy's "revolt against idealism," rejecting Hegelian holism in favor of realism and the doctrine of external relations, and helping shift subsequent philosophical attention toward more scientifically tractable, logically precise questions, including those later addressed regarding mind and knowledge. Russell would go on, over the next three decades, to develop his own distinctive answer to the mind-matter question — neutral monism — in the two books that appear later in this timeline (1921, 1927).
1913	School founded	American psychologist John B. Watson delivers his lecture "Psychology as the Behaviorist Views It" at Columbia University, published shortly after in Psychological Review; the "behaviorist manifesto" launches behaviorism as a school of psychology and rejects introspection as a scientific method. This marks a sharp break from the introspection-friendly psychology of James (1884, 1890) and Ebbinghaus, even though Watson built on their shared commitment to a strictly empirical psychology.
1921	Publication	British philosopher and logician Bertrand Russell publishes The Analysis of Mind (Allen & Unwin), seeking to reconcile psychology, philosophy, and the physical sciences — presenting his first book-length statement of neutral monism, fusing William James's neutral-stuff metaphysics with emerging behaviorism and his own causal theory of meaning, and expressing the hope that physical and psychological causal laws might one day approach unification. Russell would extend this same neutral-monist framework from the mind side to the matter side six years later in The Analysis of Matter.
1925	Philosophical work	British philosopher C. D. Broad publishes The Mind and Its Place in Nature, articulating British Emergentism — the view that mind possesses novel causal properties arising from, but not reducible to, physical organization — as a middle path between panpsychism and pure materialism, helping define problems later addressed by physicalists. The title is directly echoed nearly eight decades later in Chalmers's 2002 paper "Consciousness and Its Place in Nature," which classifies emergentism as a form of Chalmers's "Type-F monism."
1925	Publication	British philosopher and logician Bertrand Russell publishes The ABC of Relativity, a popular exposition of Einstein's special and general relativity for general readers, promoting a scientifically informed worldview — closing with a chapter on "Philosophical Consequences" — that runs alongside, and helped popularize, the broader scientific-naturalist outlook underlying his contemporaneous philosophical work on mind and matter (1921, 1927).
1927	Publication	British philosopher and logician Bertrand Russell publishes The Analysis of Matter, exploring relationships between physical science and mental phenomena through his theory of neutral monism — the view that the fundamental stuff of reality is "events" that are neither mental nor physical. Though not itself a physicalist position, Russell's claim that physics describes only the abstract structure of matter while leaving its intrinsic nature unknown later became a key reference point for the "Russellian monist" approaches to consciousness still actively debated alongside Type-A physicalism today.
1929	Manifesto	Members of the Vienna Circle — primarily Austrian sociologist Otto Neurath, German philosopher Rudolf Carnap, and Austrian mathematician Hans Hahn — publish Wissenschaftliche Weltauffassung: Der Wiener Kreis ("The Scientific Conception of the World: The Vienna Circle"), advancing scientific naturalism and opposition to metaphysical dualism by characterizing the "scientific world-conception" through its basic attitude and methods rather than fixed theses, and pursuing the unification of all science. Presented at the first international conference of logical empiricism later that year, the manifesto launched the movement that, over the next two decades (rows below), would extend physicalist reduction explicitly to psychology.
1930s–1950s	Intellectual movement	Logical positivists and analytic philosophers increasingly treat mental states as behavioral or physical phenomena, exemplified by Carnap's "Psychology in Physical Language" (1932–33), which proposes translating psychological statements into physical and behavioral terms for verifiability, and Hempel's 1949 analysis equating mental claims with behavioral dispositions. This movement directly extends the unification-of-science program announced in the Vienna Circle's 1929 manifesto from physics and the social sciences specifically into psychology, and provides the immediate philosophical soil from which Ryle's and Place's mid-century behaviorism and identity theory (rows below) grow.
1934	Publication	German-American philosopher Rudolf Carnap publishes Logische Syntax der Sprache (The Logical Syntax of Language), developing the formal/material mode distinction and arguing that if every sentence of a science can be translated into physical language, then physics, psychology, and the social sciences form one uniform science in a single physical language — reinforcing the logical positivist groundwork for physicalist interpretations of mental discourse developed more directly in his earlier "Psychology in Physical Language" papers (1932–33).
1935	Conference	German-American philosopher Rudolf Carnap participates in the First International Congress for the Unity of Science (Congrès international de philosophie scientifique) at the Sorbonne in Paris — alongside German philosopher Hans Reichenbach and Austrian philosopher Moritz Schlick, and around 170 other attendees from over twenty countries — advancing the unity of science movement and its physicalist program of encouraging the reduction of psychological explanations to physical, intersubjectively verifiable descriptions. The congress represents the international institutionalization of the program announced six years earlier in the Vienna Circle's manifesto.
1935	Publication	German-American philosopher Carl Gustav Hempel publishes "The Logical Analysis of Psychology" (originally "Analyse logique de la psychologie," Revue de Synthèse), advancing logical behaviorism by arguing that psychological statements can be translated into, and verified by, physicalist statements about behavior and physiological processes. Reprinted in English in 1949, the later translation substantially widened its influence — the 1949 date is the one usually cited in the "1930s–1950s" composite row above, but 1935 marks the paper's original appearance.
1936	Publication	British mathematician and logician Alan Turing publishes "On Computable Numbers, with an Application to the Entscheidungsproblem" in the Proceedings of the London Mathematical Society, developing the concept of a universal computing machine (the "Turing machine") to resolve Hilbert's Entscheidungsproblem — modeling the abstract machine's processes after the functional, symbol-manipulating "states of mind" of a human computer. This concept becomes the technical ancestor of the entire computational-theory-of-mind tradition that runs through this timeline, from Putnam's machine-state functionalism (1960, 1967) to Fodor's computational theory of mind (1975) and beyond.
1943	Scientific paper	American neurophysiologist Warren McCulloch and American logician Walter Pitts publish "A Logical Calculus of the Ideas Immanent in Nervous Activity" in the Bulletin of Mathematical Biophysics, proposing a mathematical model of the nervous system as a network of simple logical threshold elements — later known as artificial neurons or McCulloch–Pitts neurons — and proving that such networks could compute any logical/Boolean function. This paper directly inspired Minsky's first physical neural-network machine (SNARC, 1951, below) and laid foundations for computational accounts of cognition, artificial intelligence, and automata theory more broadly.
1948	Publication	American mathematician Norbert Wiener publishes Cybernetics: Or Control and Communication in the Animal and the Machine, helping establish information-processing approaches to mind and behavior by treating feedback, communication, and control as universal principles applying equally to machines and living organisms — including the nervous system — and coining the term "cybernetics" itself. Wiener, McCulloch, and Pitts were all central figures at the Macy Conferences that directly seeded the information-processing paradigm later institutionalized in the founding of Cognitive Science (the journal, 1977, and society, 1979) below.
1949	Publication	British philosopher Gilbert Ryle publishes The Concept of Mind, attacking Cartesian dualism as a "category mistake" and dismissing the dualist picture of mind as "the ghost in the machine," arguing that mental concepts refer to behavioral dispositions rather than to a separate non-physical substance. Ryle's logical-behaviorist attack on dualism sets the stage directly for Place's and Smart's identity theory (below), which would soon push past behaviorism by identifying mental states with brain processes rather than mere behavioral dispositions.
1950	Philosophical argument	British mathematician and logician Alan Turing publishes "Computing Machinery and Intelligence" in Mind (journal), proposing the "imitation game" — now known as the Turing test — as a behavioral criterion for machine intelligence, sidestepping the question "Can machines think?" in favor of a test based on observable conversational performance. The test is an early behavioral/functional criterion for mentality, sitting chronologically and conceptually between Ryle's behaviorism (the previous row) and the rise of full-fledged functionalism a decade later (Putnam, 1960).
1950	Publication	Austrian-American philosopher Herbert Feigl publishes "The Mind-Body Problem in the Development of Logical Empiricism" in Revue Internationale de Philosophie, an early statement defending the view that mental states are ultimately identifiable with physical processes — tracing this position back to Moritz Schlick's largely unknown 1918 identity theory within the Austrian tradition of psychophysical parallelism. This paper marks the start of the "Austrian" lineage of identity theory (Schlick–Feigl), distinct from the "Australian" lineage (Place–Smart) that develops independently later this decade, and lays groundwork for Feigl's fuller identity theory in "The 'Mental' and the 'Physical'" (1958).
1951	Scientific development	Early neural network research begins to suggest that cognitive processes may be implemented by physical computational systems, exemplified by American cognitive scientist Marvin Minsky and Dean Edmonds building SNARC (Stochastic Neural Analog Reinforcement Calculator) at Harvard — a physical machine of forty interconnected artificial (Hebbian) neurons that learned to navigate a simulated maze through reinforcement, directly inspired by the 1943 McCulloch–Pitts model above. SNARC is one of the first pioneering efforts in artificial intelligence, marking the transition of computational theories of mind from pure mathematics (Turing, McCulloch–Pitts) into working physical hardware.
1953	Publication	American psychologist B. F. Skinner publishes Science and Human Behavior, extending operant conditioning and radical behaviorism from the animal laboratory to human society — arguing that inner mental states are not denied to exist but are explanatorily irrelevant, since behavior can be fully accounted for by its functional relation to environmental history and reinforcement. The book marks behaviorism's high-water mark in psychology, right before the rows below (Place, Feigl, Smart) document its philosophical replacement by identity theory.
1956	Publication	British philosopher U. T. Place publishes "Is Consciousness a Brain Process?" in the British Journal of Psychology, arguing against both behaviorism and dualism that consciousness should instead be identified with a pattern of brain activity — an influential statement of identity theory, also known as "Australian materialism." Developed independently of, and a few years before, Smart's parallel statement of the same view (1959, below), Place's paper marks the moment philosophy of mind moves past Ryle's and Skinner's behaviorism toward direct identification of mind with brain.
1956	Publication	American philosopher Wilfrid Sellars publishes "Empiricism and the Philosophy of Mind" in Minnesota Studies in the Philosophy of Science, Vol. I, attacking the "Myth of the Given" — the idea that sensory experience can furnish foundational, non-inferential knowledge prior to and independent of any conceptual framework — and proposing his own "Myth of Jones" as an alternative naturalistic account of how the very concept of inner mental episodes could have arisen. Published the same year as Place's identity theory paper above, Sellars's essay contains the first functionalist treatment of thought and the proposal that private experiences are "theoretical posits" — directly anticipating both the functionalism (Putnam, Lewis) and the illusionism (Frankish) that appear much later in this timeline.
1958	Publication	Austrian-American philosopher Herbert Feigl publishes "The 'Mental' and the 'Physical'" in Minnesota Studies in the Philosophy of Science, Vol. 2, a major defense of the identity theory of mind arguing that the "raw feels" of direct experience are empirically identifiable with neural processes — a wide-ranging survey described by the British Journal for the Philosophy of Science as a "super-colossal" treatment of the mind-body problem. This is the mature statement of the "Austrian" identity-theory lineage Feigl began in his 1950 paper above, developed in parallel with, but independently of, the "Australian" lineage of Place (1956) and Smart (1959, below).
1959	Publication	Australian philosopher J. J. C. Smart publishes "Sensations and Brain Processes" in the Philosophical Review, defending the mind-brain identity theory by arguing that sensations are identical with brain processes — a position, alongside Place's (1956, above), that came to be known as "Australian materialism." Smart would extend and broaden this same defense four years later in "Materialism" (1963, below).
1963	Publication	Australian philosopher J. J. C. Smart publishes "Materialism" in the Journal of Philosophy, extending his 1959 defense of the mind-brain identity theory and arguing for a thoroughgoing scientific materialism that rejects dualism, phenomenalism, and behaviorism's residual anthropocentrism in favor of a worldview grounded in physics. Smart published a book the same year, Philosophy and Scientific Realism, developing the same anti-phenomenalist, anti-behaviorist position at greater length.
1963	Publication	Austrian-American philosopher of science Paul Feyerabend publishes "Materialism and the Mind-Body Problem" in the Review of Metaphysics and "Mental Events and the Brain" in the Journal of Philosophy, arguing that commonsense mental concepts are essentially non-physical in character, such that any genuine form of physicalism entails there are no mental processes or states as understood by common sense — an early and influential argument anticipating eliminative materialism, though some later scholars dispute whether Feyerabend personally endorsed eliminativism rather than merely diagnosing confused objections to materialism. Together with Rorty's paper two years later (1965, below), Feyerabend's argument predates and anticipates the Churchlands' and Stich's eliminativism by nearly two decades.
1965	Publication	Australian philosopher D. M. Armstrong publishes "A Theory of Perception" in Scientific Psychology (eds. Benjamin Wolman and Ernest Nagel), an early statement of his causal-functional account of mental states — analyzing perception in terms of the causal acquisition of beliefs about the environment rather than the passive reception of sense-data. This essay lays groundwork that Armstrong would fully develop into a comprehensive materialist theory of mind three years later in A Materialist Theory of the Mind (1968, below).
1965	Publication	American philosopher Richard Rorty publishes "Mind-Body Identity, Privacy, and Categories" in the Review of Metaphysics, defending a materialist approach to mental states by proposing the "disappearance" form of identity theory — the view that talk of sensations and other mental states may eventually be eliminated from our vocabulary altogether as neuroscience matures, rather than merely being identified with brain processes. This is an early statement of what would later be called eliminative materialism, predating Paul Churchland's and Stich's eliminativism (1979–1983, below) by fifteen to eighteen years; Rorty would extend the same line of argument in "In Defense of Eliminative Materialism" five years later (1970, below).
1967	Publication	American philosopher Hilary Putnam publishes "Psychological Predicates" (later retitled "The Nature of Mental States"), introducing the thesis of multiple realizability — that a single mental state can be realized by many different physical structures — and developing machine-state functionalism as an alternative to both logical behaviorism and the identity theory. This is the culminating statement of the functionalist project Putnam began with "Minds and Machines" (1960, above), distinct from but complementary to it.
1968	Publication	Australian philosopher David Armstrong publishes A Materialist Theory of the Mind, defending a sophisticated physicalist account of mental states — the "central-state theory," which identifies mental states with physical states of the brain defined by their causal role — and offering a comprehensive treatment of perception, belief, the will, and introspection from a materialist standpoint. This book is the full development of the causal-functional perception theory Armstrong sketched three years earlier (1965, above), and is often read as a bridge between Place/Smart-style identity theory and the causal-functional analyses (Lewis, 1972) that follow.
1970	Publication	American philosopher Richard Rorty publishes "In Defense of Eliminative Materialism" in the Review of Metaphysics, extending his 1965 "disappearance" form of identity theory (above) into a fuller defense of the view that future neuroscience may replace folk-psychological concepts with purely physiological descriptions, rather than merely identifying mental states with brain states. Together with his 1965 paper, Rorty's eliminativism predates the Churchlands' and Stich's better-known versions of the same thesis by a full decade.
1970	Publication	Australian philosopher David Armstrong publishes the essay "The Nature of Mind," extending his materialist theory of mental states (1968, above) in more accessible form — arguing that science is the proper authority on the nature of mind, and characterizing consciousness specifically as "perception or awareness of the state of our own mind," a self-scanning system within the central nervous system. This characterization of consciousness as self-scanning directly anticipates the higher-order theories of consciousness that recur much later in this timeline (e.g. Graziano, 2017–2019).
1972	Publication	American philosopher David Lewis publishes "Psychophysical and Theoretical Identifications," developing an influential functionalist analysis in which mental state terms are defined by the causal roles specified by folk-psychological platitudes — a position later known as analytic functionalism. Lewis would go on the following year to publish Counterfactuals (1973, below), whose possible-worlds apparatus underpins much of his subsequent work on mental content and causation.
1973	Publication	American philosopher David Lewis publishes Counterfactuals (Harvard University Press), developing a possible-worlds semantics for counterfactual conditionals that later underpins much of his work on mind — including his analyses of mental content and causation — though the book's primary subject is the logic of counterfactuals rather than philosophy of mind directly. This is the logical apparatus on which Lewis's 1972 functionalist analysis of mental terms (above) ultimately depends.
1974	Publication	American philosopher Thomas Nagel publishes "What Is It Like to Be a Bat?" in the Philosophical Review, arguing that conscious experience has an irreducibly subjective character — there is "something it is like" to be a given organism — that resists capture by any objective, reductive physical or functional account, and that the contemporary status of physicalism resembles a hypothesis whose truth we cannot yet conceive. This becomes, alongside Kripke's modal argument (1980, below), one of the two canonical anti-physicalist touchstones that Dennett, Chalmers, and Frankish all later position themselves against.
1975	Publication	American philosopher Jerry Fodor publishes The Language of Thought, introducing the language of thought hypothesis and arguing for the computational and representational theory of mind — that mental processes are computations defined over an internal system of mental representations ("Mentalese"). Fodor's computational architecture, developed against the backdrop of Nagel's challenge the year before, is extended eight years later in The Modularity of Mind (1983, below) and provides foundational theory for the journal and society founded in the next two rows.
1977	Journal founded	The journal Cognitive Science (journal) is founded by American AI researchers Roger Schank and Eugene Charniak together with American psychologist Allan Collins, providing a dedicated interdisciplinary outlet for psychology, artificial intelligence, linguistics, and philosophy to converge on the study of mind as an information-processing system. Two years later the same trio (with Don Norman) would found the Cognitive Science Society (1979, below), completing the field's institutionalization.
1978	Publication	American philosopher Daniel Dennett publishes Brainstorms (book), a collection of seventeen essays advancing a strongly naturalistic account of mind; the essay "Mechanism and Responsibility" contains Dennett's first articulation of the intentional stance, and "Are Dreams Experiences?" anticipates major ideas in his 1991 book Consciousness Explained. This is the opening entry in the long Dennett sequence that runs through the rest of this timeline (1984, 1987, 1988, 1991, 1992, 1995, 2003, 2005, 2013, 2016, 2021).
1978	Publication	American philosopher Ned Block publishes "Troubles with Functionalism" in Minnesota Studies in the Philosophy of Science, Vol. 9, critiquing both behaviorist and simplistic functionalist theories of mind — introducing the "homunculi-headed robot" and "China Brain" thought experiments to argue that any system functionally organized like a mind, however implemented, would (absurdly, by functionalist lights) have to count as having mental states. This is one of the most cited critiques of functionalism in the literature, providing an internal counterpoint to the functionalist program (Putnam, Lewis) within the same decade it was being developed, distinct from Searle's external attack via the Chinese Room two years later (1980, below).
1979	Society founded	The Cognitive Science Society is incorporated by American researchers Allan Collins, Roger Schank, and Don Norman, with its founding meeting held at the University of California, San Diego, giving cognitive science institutional identity as a recognized interdisciplinary field. This completes, two years after the journal's founding (above), the institutionalization of the information-processing paradigm traceable back to Wiener, McCulloch, and Pitts in the 1940s.
1979	Publication	American philosopher Paul Churchland publishes Scientific Realism and the Plasticity of Mind (Cambridge University Press), proposing a strong form of scientific realism and developing its implications for the philosophy of mind — laying foundations for the eliminative materialism he would more fully articulate two years later in "Eliminative Materialism and the Propositional Attitudes" (1981, below). Published the same year as Rorty's Philosophy and the Mirror of Nature (below), it is part of a coordinated wave of anti-foundationalist, naturalistic philosophy of mind that year.
1979	Publication	American philosopher Richard Rorty publishes Philosophy and the Mirror of Nature (Princeton University Press), criticizing traditional conceptions of mind and introspective certainty — attacking the philosophical idea of knowledge as a mental "mirroring" of a mind-external world, and arguing, drawing on Quine's attack on the analytic/synthetic distinction and Sellars's attack on the Myth of the Given (1956, above), that there is no neutral, foundational "Glassy Essence" of mind that could ground epistemology as a search for certainty. This book is the culmination of the eliminativist line of argument Rorty opened in 1965 and 1970 (above), and marks his public break with mainstream analytic epistemology.
1980	Publication	American philosopher Saul Kripke publishes Naming and Necessity (Harvard University Press; based on lectures delivered at Princeton in 1970, first published in article form in 1972), presenting modal arguments against the mind-brain identity theory — that since identity statements between rigid designators are necessary if true, and pain could exist without the corresponding brain state (or vice versa) in some possible world, pain cannot be identical to that brain state. Alongside Nagel's "what it's like" argument (1974, above), this is one of the two canonical anti-physicalist arguments that the entire later Type-A physicalist and illusionist tradition in this timeline has had to grapple with directly.
1981	Publication	American philosopher Paul Churchland publishes "Eliminative Materialism and the Propositional Attitudes" in the Journal of Philosophy, presenting several influential arguments for dropping commonsense psychology entirely — comparing folk-psychological concepts like belief and desire to the discredited concept of witches, and arguing that as neuroscience matures, the poverty of these everyday concepts will become apparent. This is the paper Churchland's 1979 book (above) explicitly lays the groundwork for, and it directly precedes Stich's parallel and equally influential eliminativism two years later (1983, below).
1983	Publication	American philosopher Stephen Stich publishes From Folk Psychology to Cognitive Science: The Case Against Belief (MIT Press), questioning traditional concepts of mental states by arguing that folk-psychological notions like belief, desire, and other common-sense concepts should not — and ultimately will not — play a significant role in the scientific study of the mind. Published the same year as Fodor's Modularity of Mind (below) and Rey's first consciousness-skepticism paper (below), this book sits at the center of a cluster of eliminativist and naturalistic work in 1983; Stich extends the same argument two years later in "Could Man Be an Irrational Animal?" (1985, below).
1983	Publication	American philosopher Jerry Fodor publishes The Modularity of Mind: An Essay on Faculty Psychology (MIT Press), reinforcing information-processing models of cognition by proposing that perceptual "input systems" are domain-specific, fast, mandatory, and informationally encapsulated modules — distinct from central cognitive processes. This extends, eight years on, the computational architecture Fodor laid out in The Language of Thought (1975, above), synthesizing results from the cognitive science field whose journal and society were founded in 1977 and 1979 (above).
1983	Publication	American philosopher Georges Rey publishes "A Reason for Doubting the Existence of Consciousness" in Consciousness and Self-Regulation (eds. Davidson, Schwartz, and Shapiro), explicitly developing illusionist-adjacent doubts about phenomenal consciousness — addressing an audience of psychobiologists to argue that introspection systematically misrepresents mental states, and that the prospects for a reductive account of consciousness cannot be properly assessed without first questioning whether the targeted phenomenon is even real as ordinarily conceived. Rey would return to this same theme five years later in "A Question About Consciousness" (1988, below), and much later as a named commentator in Frankish's 2017 illusionism volume.
1984	Publication	American philosopher Daniel Dennett publishes Elbow Room: The Varieties of Free Will Worth Wanting (based on his 1983 John Locke Lectures at Oxford), extending his naturalistic treatment of agency and consciousness by defending a compatibilist conception of free will — arguing that the common-sense conception of free will is compatible with a purely physical, biological view of human beings. This continues Dennett's naturalistic program from intentionality (1978, above) toward free will, setting up the later move to consciousness itself in Consciousness Explained (1991, below).
1985	Publication	American philosopher Stephen Stich publishes "Could Man Be An Irrational Animal?" in Synthese, extending his case that folk psychology may be a false theory subject to scientific replacement by examining how findings of systematic human irrationality from cognitive psychology threaten to undermine, rather than merely supplement, common-sense conceptions of belief and rational agency. This develops, two years on, the eliminativist project Stich opened in From Folk Psychology to Cognitive Science (1983, above) in a new direction — rationality rather than vocabulary.
1986	Publication	American philosopher Patricia Churchland publishes Neurophilosophy: Toward a Unified Science of the Mind-Brain (MIT Press), arguing that common-sense psychology should be integrated with — and may ultimately be revised or replaced by — findings from neuroscience, and establishing neurophilosophy as an interdisciplinary field bridging philosophy of mind and brain science. This book founds the field that her husband Paul Churchland would extend in A Neurocomputational Perspective (1989, below), beginning a sequence of Patricia Churchland rows (1986, 1996, 2011, 2013) running through this timeline.
1987	Publication	American philosopher Daniel Dennett publishes The Intentional Stance, the first full-scale presentation of his theory of intentionality, developing the intentional stance — a predictive strategy that explains and anticipates a system's behavior by attributing to it beliefs, desires, and rationality — as a framework applicable to humans, animals, and artificial systems alike. The intentional stance was first sketched nine years earlier in the essay "Mechanism and Responsibility" within Brainstorms (1978, above); this book is its full development, and the next Dennett row (1988, "Quining Qualia," below) turns from intentionality to qualia.
1988	Publication	American philosopher Daniel Dennett publishes "Quining Qualia" in Consciousness in Contemporary Science (eds. Anthony Marcel and Edoardo Bisiach), arguing that qualia as traditionally conceived — special, ineffable, intrinsic, directly apprehensible properties of experience — do not exist, and that the intuitions supporting them rest on confused thought experiments rather than genuine phenomena. This is arguably the most direct ancestor of Frankish's illusionism (2016, below), since "denying qualia exist" is exactly the illusionist move; Dennett would extend the same argument three years later in Consciousness Explained (1991, below).
1988	Publication	American philosopher Georges Rey publishes "A Question About Consciousness" in Perspectives on Mind (eds. Herbert R. Otto and James A. Tuedio), developing the view that conscious experience may involve systematic introspective error — anticipating later illusionist theories by arguing that our sense of a "strong," ineffable phenomenal consciousness may be an illusory projection of innate, involuntary responses rather than evidence of a genuine non-physical or otherwise mysterious property of mind. This is Rey's second statement of consciousness-skepticism, following his 1983 paper above by five years and preceding his role as a commentator in Frankish's 2017 illusionism volume.
1989	Publication	American philosopher Paul Churchland publishes A Neurocomputational Perspective: The Nature of Mind and the Structure of Science (MIT Press), arguing that solving central problems in the philosophy of science requires drawing on the emerging sciences of the mind-brain, and applying concepts from neural-network ("connectionist") models to recast longstanding philosophical problems — including a defense of eliminative materialism against Frank Jackson's knowledge argument. This extends Paul Churchland's eliminativist program (1979, 1981, above) into the connectionist framework his wife Patricia had founded three years earlier (1986, above); he would extend it again, for a general audience, in The Engine of Reason, the Seat of the Soul (1995, below).
1991	Publication	American philosopher Daniel Dennett publishes Consciousness Explained, introducing the Multiple Drafts Model of consciousness and rejecting the "Cartesian Theater" — the idea that there is a single central locus in the brain where information is gathered for presentation to a unified subject of experience — proposing instead that consciousness consists of many parallel, content-fixing processes occurring at different times and places in the brain, with no single narrative being uniquely "the" stream of consciousness. This is Dennett's major defense of a Type-A-style approach to consciousness, extending the qualia-skepticism of "Quining Qualia" (1988, above) into a full positive theory, which Dennett and Kinsbourne would extend the following year (1992, below).
1992	Publication	American philosopher Daniel Dennett and Canadian neuropsychologist Marcel Kinsbourne publish "Time and the Observer: The Where and When of Consciousness in the Brain" in Behavioral and Brain Sciences, extending the Multiple Drafts Model introduced in Consciousness Explained (1991, above) — arguing that there is no single, determinate moment at which a perceptual event becomes conscious, and that the seeming choice between "Orwellian" (retroactive) and "Stalinesque" (proactive) editing of experience is itself an artifact of the rejected Cartesian Theater model. The paper provoked substantial commentary, including a notable response from Ned Block, whose own critique of functionalism (1978, above) had already established him as a major internal critic of physicalist theories of mind.
1995	Publication	American philosopher Daniel Dennett publishes Darwin's Dangerous Idea: Evolution and the Meanings of Life, extending evolutionary explanations to cognition, consciousness, language, and morality by arguing that natural selection is a "universal acid" — a mindless, algorithmic process capable of generating Design without a Designer — and that minds themselves are products of this same algorithmic process rather than requiring an unexplained "skyhook." This continues Dennett's naturalistic program from consciousness (1991, above) into evolutionary theory, directly extending the Darwinian thread on emotional expression opened by Darwin himself well over a century earlier (1872, above).
1995	Publication	American philosopher Fred Dretske publishes Naturalizing the Mind (based on his 1994 Jean Nicod Lectures, MIT Press), advancing a representational theory aimed at explaining consciousness within a physicalist framework — arguing that the qualitative, phenomenal "what-it-is-like" aspects of experience are identical with external, real-world properties that experience represents objects as having, and combining this with an evolutionary account of sensory representation to give a fully naturalistic treatment of phenomenal consciousness. Published the same year as Tye's parallel representationalist program (below), the two theories were arrived at independently but are extremely similar.
1995	Publication	American philosopher Paul Churchland publishes The Engine of Reason, the Seat of the Soul: A Philosophical Journey into the Brain (MIT Press), defending a strongly neurobiological account of cognition for a general audience, summarizing results from neuroscience and artificial neural network research to address how the brain sustains a thinking, feeling, self-conscious person. This extends the connectionist framework of A Neurocomputational Perspective (1989, above) to consciousness, machine consciousness, and moral cognition, completing a three-stage Paul Churchland sequence: 1979 → 1981 → 1989 → 1995.
1995–2000	Theoretical development	American philosopher Michael Tye develops representationalist theories of consciousness in Ten Problems of Consciousness (1995) and Consciousness, Color, and Content (2000), identifying phenomenal character with a special kind of intentional content (the "PANIC" theory: poised, abstract, nonconceptual intentional content) — a reductive approach often discussed alongside Type-A and Type-B physicalist strategies. Tye would extend this program to the unity of consciousness and personal identity eight years later in Consciousness and Persons (2003, below).
1996	Concept popularized	Australian-American philosopher David Chalmers publishes The Conscious Mind, expanding at book length on the "hard problem of consciousness" he had coined the previous year in his paper "Facing Up to the Problem of Consciousness" (1995) — the distinction between "easy problems" explicable via standard cognitive-scientific methods and the "hard problem" of explaining subjective experience itself. This framing of the problem provoked an immediate, same-year rebuttal from Patricia Churchland (below), and would later be formalized into the full Type-A/B/C taxonomy in Chalmers's 2002 paper (below).
1996	Publication	American philosopher Patricia Churchland publishes "The Hornswoggle Problem" in the Journal of Consciousness Studies, criticizing appeals to irreducible phenomenal properties by arguing directly against Chalmers's hard problem/easy problems distinction (above) — contending that using current ignorance as a premise for what we can never discover, and "I-cannot-imagine" arguments, are logical flaws rather than genuine metaphysical insights. This direct, same-year rebuttal to Chalmers gives the timeline an explicit philosophical clash right at the moment the hard problem enters wide circulation.
1999	Publication	British psychologist Susan Blackmore publishes The Meme Machine (Oxford University Press), promoting a naturalistic account of mind and selfhood influenced by Dennett — arguing that the "self" is itself a "selfplex," a complex of memes rather than a unified entity, and that there is no single center of consciousness corresponding to Dennett's "Cartesian Theatre." Blackmore later appears as one of the named commentators in Frankish's 2017 illusionism volume (below), so this book shows her naturalistic, eliminativist-about-the-self views predating and feeding directly into her later illusionist engagement.
2002	Classification introduced	Australian-American philosopher David Chalmers publishes "Consciousness and Its Place in Nature," introducing a taxonomy of materialist and dualist positions on consciousness — Type-A, Type-B, and Type-C materialism, plus Type-D and Type-E dualism and Type-F monism — and defining Type-A materialists as those who deny that there is a genuine explanatory gap between physical facts and consciousness. This taxonomy, six years after the hard problem itself was popularized (1996, above), gives this entire timeline its organizing term, and its title is a direct echo of C. D. Broad's 1925 book above.
2002	Publication	British philosopher David Papineau publishes Thinking About Consciousness (Oxford/Clarendon Press), defending a reductive materialist response to anti-physicalist arguments — but specifically as a sophisticated statement of Type-B materialism rather than Type-A (using Chalmers's just-published taxonomy above), conceding that there is a genuine conceptual gap between mental and physical vocabularies while denying that this conceptual gap implies any actual ontological dualism. Papineau's "Phenomenal Concept Strategy"-style defense is exactly the kind of position Stoljar would name and critique three years later (2005, below).
2003	Publication	American philosopher Daniel Dennett publishes "Who's on First? Heterophenomenology Explained" in the Journal of Consciousness Studies, further defending heterophenomenology as a scientific method for studying consciousness that treats first-person verbal reports as data to be explained — akin to useful theoretical fictions in physics — without positing irreducible, ineffable qualia. This responds directly to challenges (from Chalmers, Goldman, and Velmans) about what does and doesn't count as heterophenomenology, continuing a defensive, elaborative project Dennett would extend twice more (2005, 2007).
2003	Publication	German philosopher Thomas Metzinger publishes Being No One: The Self-Model Theory of Subjectivity (MIT Press), defending the view that the self is a transparent representational construct — arguing that no such things as selves exist in the world; all that exists are phenomenal selves as they appear in conscious experience, with the phenomenal self being not a thing but an ongoing process constituted by the content of a "transparent self-model." This is the rigorous, technical statement preceding Metzinger's own popular-audience companion volume, The Ego Tunnel (2009, below).
2003	Publication	American philosopher Michael Tye publishes Consciousness and Persons: Unity and Identity (MIT Press), extending his representationalist program to the unity of consciousness and personal identity — arguing that unity consists in relations between the contents of experience rather than between separate experiences themselves, and drawing on representationalism to address the split-brain phenomenon and the nature of persons. This is the third stage of Tye's representationalist trilogy, following Ten Problems of Consciousness (1995) and Consciousness, Color, and Content (2000) above.
2005	Publication	Australian philosopher Daniel Stoljar publishes "Physicalism and Phenomenal Concepts," coining the term "Phenomenal Concept Strategy" for an existing physicalist defense (of the kind Papineau had given in 2002, above) — that the apparent gap between physical and phenomenal truths stems from special features of phenomenal concepts rather than from a real metaphysical gap — and arguing that no version of the strategy succeeds, proposing instead a rival "missing concept strategy." This paper, naming and critiquing rather than defending the strategy, accelerated the very skepticism that fed into Frankish's illusionism a decade later (2016, below).
2005	Publication	American philosopher Daniel Dennett publishes Sweet Dreams: Philosophical Obstacles to a Science of Consciousness (based on his 2001 Jean Nicod Lectures), directly challenging the hard problem framework by extending his attack on qualia — using the metaphor of philosophical zombies and addressing popular thought experiments — and revising his "multiple drafts" theory of consciousness in light of empirical advances since Consciousness Explained (1991, above). This is the second of three consecutive Dennett entries continuing the same defensive, elaborative project across the early-to-mid 2000s (2003, 2005, then "Heterophenomenology Reconsidered" in 2007), directly preceding his explicit illusionism endorsement in 2016 (below).
2009	Publication	German philosopher Thomas Metzinger publishes The Ego Tunnel: The Science of the Mind and the Myth of the Self (Basic Books), arguing that the self is a representational construct generated by the brain — no such thing as a "self" exists as an independent entity; rather, the conscious self is the content of an internal model ("Ego Tunnel") created by the brain to represent and navigate the world. This is the accessible, general-audience companion to Metzinger's more technical Being No One (2003, above), and a major eliminativist-about-the-self statement directly anticipating illusionism's later treatment of phenomenal consciousness as a useful but non-veridical internal model.
2010	Publication	French neuroscientist Stanislas Dehaene and colleagues (Zylberberg, Fernandez Slezak, Roelfsema, Sigman) publish "The Brain's Router: A Cortical Network Model of Serial Processing in the Primate Brain" in PLOS Computational Biology, providing computational support for global workspace theories of conscious access compatible with Type-A physicalism — modeling how a small set of densely-connected "hub" regions in prefrontal and parietal cortex serializes access to perceptual information. This is a key mechanistic prediction later elaborated at book length in Dehaene's Consciousness and the Brain (2014, below).
2011	Publication	American philosopher Patricia Churchland publishes Braintrust: What Neuroscience Tells Us About Morality, arguing that morality originates in the biology of the brain rather than in religion, pure reason, or absolute rules — locating its roots in a "neurobiological platform of bonding," rooted in mammalian care for offspring and shaped by oxytocin, evolutionary pressure, and culture. This is the first of three late-career Patricia Churchland books extending her neurophilosophy program (1986, above) toward morality specifically, followed by Touching a Nerve (2013) and Conscience (2019).
2011	Publication	American philosopher Eric Schwitzgebel publishes Perplexities of Consciousness (MIT Press), advancing sustained skepticism about introspective reliability — through detailed case studies (dream color, emotional phenomenology, peripheral vision, echolocation, the existence of "cognitive phenomenology") arguing that introspection produces firm but false beliefs about our own conscious experience even in normal, favorable circumstances, not merely unusual ones. This provides empirical and philosophical support for illusionist approaches to consciousness by undermining the Cartesian assumption that we have privileged, reliable access to our own phenomenal states, and directly underlies the 2015 Schwitzgebel–Kammerer exchange below.
2012	Research trend	Predictive coding becomes a major framework in cognitive neuroscience, supporting mechanistic accounts of conscious experience, exemplified by neuroscientists André Bastos, W. Martin Usrey, Rick A. Adams, George R. Mangun, Pascal Fries, and Karl Friston's "Canonical Microcircuits for Predictive Coding" in Neuron — proposing specific cortical circuitry (distinct populations of prediction and prediction-error neurons across hierarchical levels) as the biological implementation of predictive coding. This neuroscience-first contribution precedes, and is later joined by, the philosophical elaboration of predictive processing in Clark's "Embodied Prediction" (2015, below).
2013	Publication	American philosopher Patricia Churchland publishes Touching a Nerve: The Self as Brain, continuing her long-running neurophilosophical program (1986, 2011, above) — arguing that the self, including consciousness and moral feeling, is identical to brain activity and rejecting non-physical explanations of mind in favor of ongoing co-evolution between philosophy and neuroscience. She would extend this same program to moral intuition specifically six years later in Conscience (2019).
2013	Publication	American philosopher Daniel Dennett publishes Intuition Pumps and Other Tools for Thinking (W. W. Norton), revisiting arguments against intrinsic qualia and Cartesian intuitions through seventy-seven "imagination-extenders and focus-holders" spanning evolution, meaning, mind, and free will, including the argument that realist accounts of qualia lead to an absurd infinite regress of homunculi perceiving their own perceiving. This sits between Sweet Dreams (2005, above) and Dennett's explicit adoption of the "illusionism" label three years later (2016, below), restating and refining his qualia-skepticism.
2014	Publication	French neuroscientist Stanislas Dehaene publishes Consciousness and the Brain: Deciphering How the Brain Codes Our Thoughts, defending a neuroscientific explanation of conscious access through the Global Neuronal Workspace model — proposing that conscious access occurs when information ignites a self-sustaining, brain-scale state of activity in prefrontal-parietal networks, making that information globally available for reasoning, memory, and verbal report. This is the full book-length elaboration of the mechanistic prediction modeled computationally four years earlier (2010, above).
2015	Publication	French philosopher François Kammerer publishes "How a Materialist Can Deny That the United States Is Probably Conscious — Response to Schwitzgebel" in Philosophia, beginning a body of work that becomes influential in the defense and analysis of illusionism — responding directly to Eric Schwitzgebel's argument (below) that materialism implies group entities like the United States are probably conscious, by denying the phenomenal realism on which that argument depends. Schwitzgebel would reply in turn the following year ("Is the United States Phenomenally Conscious? Reply to Kammerer," 2016), completing a tight three-paper exchange.
2015	Publication	American philosopher Eric Schwitzgebel publishes "If Materialism Is True, the United States Is Probably Conscious" in Philosophical Studies, arguing that common assumptions about conscious experience are often mistaken — pressing materialists to extend the criteria they already accept for rabbit and alien consciousness to spatially distributed, informationally integrated group entities, concluding that a materialist who accepts those other cases should also accept that the United States probably meets plausible materialistic criteria for consciousness. This provoked Kammerer's direct response (above) the same year, and Schwitzgebel's own further reply the year after.
2016	Publication	British philosopher Keith Frankish publishes "Illusionism as a Theory of Consciousness" as the target article for a special issue of the Journal of Consciousness Studies, coining the term "illusionism" and arguing that phenomenal consciousness, as usually conceived, is illusory — proposing that the hard problem be replaced by the "illusion problem" of explaining why experience seems to have phenomenal properties. Though Frankish coined the term, he was by no means the first to hold the position: Dennett, Farrell, Feyerabend (1963, above), Humphrey, Pereboom, Rey (1983, 1988, above), and Rorty (1965, 1970, above) had all defended similar views before him; the special issue, including Dennett's commentary (below), was first tested in live debate at the 2014 consciousness cruise (above).
2016	Publication	American philosopher Daniel Dennett publishes "Illusionism as the Obvious Default Theory of Consciousness" as a commentary in Frankish's Journal of Consciousness Studies special issue (above), arguing — using a parallel with stage magic — that illusionism should be treated not as an extreme alternative but as the conservative front-runner theory of consciousness, to be developed in detail and abandoned only if it demonstrably fails to account for the phenomena. Dennett traces the seeds of illusionism back to Place's "Is Consciousness a Brain Process?" (1956, above) and Smart's elaborations (1959, 1963, above), giving this timeline's own identity-theory rows new retrospective significance as illusionism's distant ancestors.
2017	Research trend	Integrated computational and neuroscientific models increasingly challenge the need for non-physical explanations of subjective experience, exemplified by American neuroscientist Michael Graziano's "The Attention Schema Theory: A Foundation for Engineering Artificial Consciousness" — proposing that the attention schema theory is fully mechanistic, explains how an information-processing brain comes to claim it possesses non-physical subjective awareness without that awareness needing to be real, and offers a possible blueprint for engineering machine consciousness on this basis. Graziano would extend this same theory two years later into an explicit reconciliation with global workspace, higher-order, and illusionist theories (2019, below).
2017	Edited volume	British philosopher Keith Frankish edits Illusionism as a Theory of Consciousness (Imprint Academic), reprinting his 2016 target article (above) in book form alongside nearly twenty commentaries from supporters and critics — including Daniel Dennett, Nicholas Humphrey, Derk Pereboom, Georges Rey, Susan Blackmore, Philip Goff, and Jesse Prinz — and his reply to commentators, "Not Disillusioned." This reunites several figures already in this timeline (Rey, 1983/1988; Blackmore, 1999; Goff and Prinz, present at the 2014 consciousness cruise above) as named participants in the same debate.
2019	Publication	British philosopher Keith Frankish publishes "The Consciousness Illusion" in Aeon, restating his illusionist case for a general audience — that phenomenal consciousness, as usually conceived, doesn't exist, and that introspection systematically misrepresents complex but non-phenomenal brain processes as having special, ineffable qualities. This is the accessible companion to two more technical 2019 papers Frankish published the same year ("The Meta-Problem is The Problem of Consciousness," below, and others), continuing the public-facing thread he opened with the 2016 target article (above).
2019	Publication	American neuroscientist Michael Graziano, Arvid Guterstam, Branden Bio, and Andrew Wilterson publish "Toward a Standard Model of Consciousness," arguing that the attention schema theory, global workspace theory, higher-order thought theory, and illusionism are not rival accounts but complementary pieces of a single coherent explanation of consciousness, reconciling them within a Type-A-compatible framework. This extends Graziano's 2017 mechanistic foundation paper (above) into an explicit synthesis across four major research programs that otherwise appear as separate threads throughout this timeline's 2010s–2020s rows.
2019	Publication	French philosopher François Kammerer publishes "The Illusion of Conscious Experience" in Synthese (alongside "How Rich Is the Illusion of Consciousness?" in Erkenntnis and "The Consciousness Meta-Problem and the Evidential Approach" in the Journal of Consciousness Studies), helping formalize illusionism within contemporary philosophy of mind by directly confronting its most counterintuitive feature — that the thesis "consciousness does not exist, even though it seems to exist" is widely judged uniquely absurd. This is Kammerer's major formalizing statement, following his 2015 exchange with Schwitzgebel (above) by four years.
2019	Publication	British philosopher Keith Frankish publishes "The Meta-Problem is The Problem of Consciousness" in the Journal of Consciousness Studies (as part of a special issue responding to David Chalmers's "meta-problem of consciousness"), refining illusionism by arguing that once all phenomenal intuitions about consciousness are explained away in topic-neutral terms, nothing further remains to be explained — so that justifying continued belief in consciousness itself would require committing to substance dualism or a mysterious intrinsic subjectivity. The same special issue included responses from Graziano, Humphrey, Kammerer, Levine, Papineau, Pereboom, and Rosenthal — several of whom appear elsewhere in this timeline as independent contributors.
2020	Intellectual trend	Illusionism becomes an established research program discussed alongside higher-order theories, global workspace theories, and predictive-processing accounts, prompting German philosopher Wanja Wiese to argue in Neuroscience of Consciousness that the field's proliferation of competing frameworks calls not for another rival theory but for "a minimal unifying model" capable of integrating their genuine insights. This call for unification directly anticipates the Seth and Bayne survey two years later (2022, below) and the Kuhn taxonomy four years later (2024, below).
2021	Publication	American philosopher Daniel Dennett publishes "The User-Illusion of Consciousness" in the Journal of Consciousness Studies, continuing to develop illusionist responses to the hard problem by arguing that consciousness, like a computer's user interface, presents the brain's underlying operations to itself in a simplified, useful form that need not resemble the trillions of micro-level neural transactions actually occurring beneath it. This was one of Dennett's last papers before his death in April 2024, closing out a Dennett sequence running from 1978 through 2021 — the longest single-author thread in this timeline.
2022	Research trend	Growing discussion emerges concerning whether advanced artificial intelligence systems could exhibit forms of consciousness explainable entirely in computational terms, sparked publicly by Google engineer Blake Lemoine's claim in June 2022 that the company's LaMDA language model was sentient — a claim Google rejected and most AI researchers dismissed, but which provoked sustained debate about the relationship between sophisticated linguistic behavior and genuine consciousness. This episode directly prompted Chalmers's more rigorous philosophical engagement the following year (2023, below).
2023	Intellectual trend	Large language models and advances in artificial intelligence renew debates about whether apparently conscious behavior can emerge from purely computational systems, exemplified by Australian-American philosopher David Chalmers's widely discussed paper "Could a Large Language Model be Conscious?" — prompted partly by the LaMDA controversy the year before (above) — which surveys obstacles to LLM consciousness (lack of recurrent processing, a global workspace, and unified agency) while taking seriously the prospect that successor systems might overcome them. This paper would itself be echoed two years later in Bengio and Elmoznino's "Illusions of AI Consciousness" (2025, below).
2024	Research trend	Empirical consciousness research increasingly focuses on functional, computational, and representational mechanisms rather than irreducible phenomenal properties, exemplified by a special issue of the European Journal of Neuroscience, "New Trends in the Empirical Study of Consciousness: Measures and Mechanisms" (eds. Athina Tzovara et al.), gathering twelve studies on the computational and experimental mechanisms and measures underlying conscious processing. The same year also saw Robert Lawrence Kuhn's pluralistic "Landscape of Consciousness" survey, cataloguing over 200 rival theories — a reminder that the mechanistic turn this row documents coexists with, rather than displaces, a still highly pluralistic field.
2025	Publication	Canadian computer scientist Yoshua Bengio and Eric Elmoznino publish "Illusions of AI Consciousness" in Science, arguing that apparent signs of consciousness in AI systems are best explained as illusions arising from how such systems represent and report on themselves — continuing to strengthen naturalistic and illusionist approaches associated with contemporary Type-A physicalism by extending them explicitly to artificial systems. This directly extends Chalmers's 2023 survey (above) two years on, with a major AI researcher rather than a philosopher now making the illusionist case for AI specifically.
2020s	Research trend	Type-A physicalist and illusionist approaches gain renewed scientific grounding through computational and neuroscientific theories of consciousness — including predictive processing, global workspace theory, higher-order theories, and (for AI applications) large language models — which Michael Graziano's attention schema theory (2017, 2019, above) has explicitly sought to reconcile with illusionism. This closing composite row ties together every major 2010s–2020s thread in this timeline: Dehaene's global workspace (2010, 2014), Bastos et al.'s predictive coding (2012), Graziano's reconciliation (2017, 2019), and the AI-consciousness debates (2022–2025) — situating Type-A physicalism within the still-pluralistic field documented by Kuhn (2024, above).

Visual and numerical data

Google Scholar

Number of Results by Decade

Decade	Number of Results
1900s	8
1910s	13
1920s	20
1930s	128
1940s	141
1950s	233
1960s	435
1970s	1,280
1980s	2,210
1990s	4,700
2000s	10,200
2010s	17,000
2020-2026	14,400

Google trends

The chart below shows Google Trends data for "type A physicalism" and "type B physicalism" (search terms) alongside "Physicalism" (Topic), worldwide, from 2004 to the present, when the screenshot was taken. While the specific technical terms "type A physicalism" and "type B physicalism" register no measurable search volume on their own (consistent with their status as specialist terms confined to academic philosophy), the broader "Physicalism" topic shows sustained worldwide search interest throughout the period, averaging 21, with a fluctuating pattern and a pronounced spike around 2025 — suggesting that while Chalmers's specific A/B/C taxonomy remains a niche term, the underlying topic of physicalism commands consistent public and academic interest over the full period covered by this timeline.

Google Ngram Viewer

The chart below shows Google Ngram Viewer data for "materialism," "physicalism," and "dualism" in the English-language book corpus, from 1800 to 2022. "Materialism" has been the dominant term throughout the period, rising steadily from the early 19th century — consistent with this timeline's Enlightenment and 19th-century rows (La Mettrie, Büchner, Lange) — and accelerating sharply from the 1980s onward. "Physicalism," the more technical term preferred in analytic philosophy of mind since the mid-20th century, registers almost no usage before 1900 and remains the least common of the three terms throughout, though it too shows a modest rise after 2000. Notably, "dualism" has risen even more steeply than "physicalism" since the 1980s, nearly converging with "materialism" by 2020 — a reminder that even as physicalist approaches have gained ground philosophically (as this timeline documents), dualism remains a heavily discussed term in the literature, consistent with the still-pluralistic state of the field this timeline's later rows describe.

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