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Debate

What Is Consciousness?

That experience depends on the brain is beyond doubt: anaesthesia switches it off, and damage to particular regions takes away particular parts of it. But why should physical processes feel like anything at all – or is that question itself a mistake?

Seeing red, feeling pain or tasting coffee is like something for the one who experiences it. Neuroscience can say ever more precisely which brain activity accompanies such experiences, but why any of this activity is accompanied by experience at all remains disputed – and the answer matters for how we treat patients who cannot respond, animals and possibly machines. In 1998 the neuroscientist Christof Koch bet the philosopher David Chalmers that the neural basis of consciousness would be clearly identified within 25 years; in 2023 he conceded the bet. In the same year the first results of an “adversarial collaboration”, in which two leading theories were tested against predictions agreed in advance, were presented, and more than a hundred researchers called one of them, integrated information theory, pseudoscience – a charge others rejected as damaging to the whole field. Philosophers, meanwhile, disagree whether consciousness poses a deep metaphysical puzzle, a scientific task like any other or, in part, an illusion.

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Positions

The hard problem

Nagel argued in 1974 that an organism is conscious if there is something it is like to be that organism – and that no objective, physical description, however complete, captures what it is like to be a bat. Frank Jackson’s thought experiment (1982) imagines Mary, a scientist who knows every physical fact about colour vision but has spent her life in a black-and-white room: does she learn something new when she first sees red? Chalmers (1995) distinguishes the “easy problems” of explaining functions such as attention, discrimination and verbal report from the hard problem of why these functions are accompanied by experience at all. Since beings physically just like us but without any experience seem conceivable, he concludes that consciousness cannot be derived from physics alone and may have to be accepted as a fundamental feature of the world.

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Consciousness is a brain process

Place (1956) and Smart (1959) proposed that sensations simply are brain processes, just as lightning turned out to be an electrical discharge: two descriptions, one thing. Physicalists today grant that there is a gap in our concepts but deny that there is a gap in the world. Lewis (1988) argued that Mary, on leaving her room, gains new abilities – to recognise, remember and imagine red – rather than knowledge of a non-physical fact; others, such as Brian Loar and David Papineau, hold that she acquires a new, “phenomenal” concept of a physical state she already knew about. Jackson himself later rejected his own argument and became a physicalist.

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Experience as an illusion

Illusionists such as Dennett and Keith Frankish (2016) hold that the hard problem rests on a mistaken picture of the mind. Our brains represent their own states as having ineffable, private qualities – “qualia” – but nothing has such qualities; what needs explaining is why it seems to us that it does. Chalmers calls this the “meta-problem” of consciousness and thinks it deserves study, while doubting that solving it would dissolve the hard problem. Galen Strawson (“The Consciousness Deniers”, 2018) calls the denial of experience the most foolish claim anyone has ever advanced; Dennett replied that he does not deny that we are conscious, only that consciousness has the properties philosophers have ascribed to it.

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Mind in matter

Russell observed in The Analysis of Matter (1927) that physics describes matter only by its structure and causal relations and says nothing about its intrinsic nature. Panpsychists such as Galen Strawson (2006) and Philip Goff (Galileo’s Error, 2019) take up this point: perhaps the intrinsic nature of matter is itself experiential, at least in rudimentary form, and complex consciousness is built up from it. This would fit experience into the natural world without either denying it or adding a separate mental substance; Whitehead’s process philosophy had already understood the basic events of nature as moments of feeling. The main objection is the “combination problem”, raised in essence by William James in 1890: how could many tiny subjects add up to a single, unified point of view?

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A biological phenomenon for science

Searle’s biological naturalism treats consciousness as a higher-level feature of the brain, caused by neurobiological processes much as digestion is caused by processes in the stomach – neither a separate substance nor an illusion, but a question for neuroscience. Anil Seth (Being You, 2021) proposes setting the hard problem aside in favour of the “real problem”: explaining, predicting and controlling the properties of experience, which he ties to the brain’s predictive regulation of the living body. The science is divided between rival theories – global workspace theory, integrated information theory, higher-order and predictive theories. In the adversarial collaboration published in Nature in 2025, the results bore out some predictions of the global workspace and integrated information theories and contradicted others; the same year, critics argued in Nature Neuroscience that the core claims of integrated information theory cannot be tested – a verdict its proponents and several other researchers rejected.

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As of 10/2026. Summaries for orientation – the sources give the full arguments. · How Agora is made

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