Science has shown that water is two molecules of hydrogen for one of oxygen; that lightning is electrostatic discharge; and that heat is the movement of molecules – so surely it can tell us what consciousness consists of. No. As Philip Goff puts it, “nothing is more certain than consciousness, and yet nothing is harder to incorporate into our scientific picture of the world”. More than 300 years after the 16th-century scientific revolution, the very thing we are most intimately immersed in remains (scientifically) a mystery. Galileo’s Error offers a brilliant introduction to the problem that tops the scientific and philosophical agenda, and a provocative putative solution to it.

That there is a problem at all, Goff argues, is the legacy of the greatest 16th-century scientist and of how he conceived the methodology of science. Galileo announced that, in pursuing an objective account of reality, we should investigate as far as possible things in themselves, and only the qualities that could not “by any stretch of my imagination” be separated from them: their shape, size, weight, degree of movement and number – qualities that are mathematically measurable, accessible to reason and untainted by the bias of a sensory system. As for tastes, smells, colours, feels (those qualities that, “if the living creature were removed…would be wiped away and annihilated”), Galileo claimed that they “reside only in the consciousness”, the result of external stimuli. What, then, and where is consciousness? Galileo, like Descartes, treated our perceptions of the world as somehow outside all the things we perceive and, therefore, exempt from scientific laws.

But in effect, this sets up two systems – mental and physical – and a mystery about how they can interact.

As Goff says, if even the most advanced neuroscientists look at a functioning brain, all they observe is neurons firing. Thoughts, emotions and sensations “don’t seem to show up”, only correlations between what the brain-owner is thinking or feeling and the areas of the brain that “light up” (because, arguably, they are significantly more “activated” than others) on an fMRI scan. Correlation is not identity, nor does it help to say that brain processes “produce” experiences. Either way, the neuron-firing and the mental state seem to be distinguishable from one another, to “come apart”, as philosophers say. In theory, the owner of the observed brain could be having all the brain processes she’s having and yet be a zombie or a robot behaving like a sentient creature.

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Like most other philosophers, Goff is loath to adopt the mind-body dualist solution of Descartes and Galileo. That, as he says, seems to make me a manipulator of the drone that is my body, but with a key difference: experts know how a drone works (and anatomists know how nerves and muscles work), but no one can account for how my intending to raise my arm triggers the process of its rising. Intentions and physical stuff seem to belong to different causal provinces.

Some heroic philosophers, such as the wonderful David Chalmers, opt for “naturalistic dualism”, postulating future psycho-physical laws for what is, meanwhile, necessarily anomalous. Many simply throw the baby out with the bathwater and declare the notion of having feelings, thoughts, desires – our whole mental life – to be an illusion, part of a primitive and inadequate theory (folk psychology) that will soon be superseded by an exact science.

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Goff was once one of these eliminative materialists, and he engagingly recounts the epiphany that changed his mind. More academically, he appeals to the so-called “knowledge argument”. This thought experiment envisages Mary, the world expert on the science of colour, as somehow sequestered from actually perceiving colours herself (she lives in a black and white room and is presumably unable to see her own blood). Materialists are obliged to say that she has a complete science of colour. Their opponents argue that if she emerges from the room and actually sees coloured objects, then her knowledge of colour will be increased. The arch-materialist Daniel Dennett responds that it won’t: Mary would have been able to discriminate colours already, since she is thoroughly cognisant of what physical impression each of them would make on her nervous system. If presented with a blue banana, she would know that she has been tricked and that bananas should be yellow. Dennett seems to envisage a future reality in which conscious awareness has been abrogated, and Mary would be holding a standard handy instrument for reading her own and other people’s brains, and for deducing what they might once (when using now-obsolete “folk psychology”) have said that they saw. But why bother to develop superfluous brain-reading technology? Why on earth, unless colour experiences intrigued and perplexed us, would a theory of colour have arisen in the first place? In an admirably understated way, Goff conveys this sort of exasperation, and reminds us that our “illusions” (the qualia, what-it-is-likeness, of experience) are in fact a tremendous evolutionary success, and beautiful as well as useful.

There seems to be an impasse between materialism and dualism, but Goff blithely sails through it. By way of quantum mechanics, time travel and Sperry’s “divided brain” experiments, he lucidly (although without patronising the reader or diluting the argument) reaches the conclusion that everything is conscious: panpsychism. He refers us to the now-neglected physicist Arthur Eddington, who in 1928 lamented that scientific explanation consists entirely of what he calls “pointer readings”, or explaining the relationships between properties and things. It tells us not what things are but only what they do – the measurements, laws, causes and effects of matter, but not their intrinsic nature. Yet, argues Eddington, “in one case – namely for the pointer readings of my own brain – I have an insight which is not limited to the evidence of the pointer readings. That insight shows that they are attached to a background of consciousness…We are acquainted with an external world because its fibres run into our own consciousness.” Consciousness in fact is not something to be squeezed into the world, but its very essence.

This is an exhilarating idea – it turns the problem on its head, makes consciousness not something private and “inside”, recalcitrant to observation, but its immediate source and habitation; makes us part of a conjointly conscious world. The trouble is, even if panpsychism accommodates qualia, our mental lives comprise not only feelings and sensations, but thoughts that are about something (whatever we are observing, remembering, conjecturing, wishing and so on). That sort of container quality of consciousness (technically called “intentionality”) remains unaccounted for.

Anyway, even if panpsychism could count as encompassing qualia, its details, and how these are to be ascertained, still need a great deal of working out, as Goff admits. Are socks and rocks conscious, or do they contain units of consciousness, or proto-consciousness? In which case, how would the units combine to make up a mental state or a long-term mind? Some things are clearly more conscious than others, but what is a partial state of consciousness? Is it in some way measurable? We seem to be cast back on to the obdurately third-person nature of scientific enquiry. Maybe Galileo was not in error, after all, and scientists have no choice but to adopt “the view from nowhere” that excludes consciousness.

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Jane O’Grady is a co-founder of the London School of Philosophy and taught philosophy of psychology at City, University of London. She is also the author of Enlightenment Philosophy in a Nutshell: The complete guide to the great revolutionary philosophers, including René Descartes, Jean-Jacques Rousseau, Immanuel Kant, and David Hume (2019).

Galileo’s Error: Foundations for a New Science of Consciousness
By Philip Goff
Penguin, 256pp, £14.99
ISBN 9781846046018
Published 7 November 2019

Philip Goff, assistant professor of philosophy at Durham University, spent the first 18 years of his life in Liverpool and subsequently lived in London, Leeds, Birmingham, Cracow and Budapest, but now thinks he will settle in Durham. He did an undergraduate degree at the University of Leeds “in the dying embers of the 20th century”, he says, as part of “the last cohort to get free education” and now doubts whether he “would’ve gone to university if I’d had to pay fees”.

Although Goff had been long “obsessed with the problem of consciousness”, he found that no one at Leeds “shared [his] views”, so he “went off to Poland to teach English as a foreign language”. It was there that he “happened upon an article by the philosopher Thomas Nagel about ‘panpsychism’”, which, he believed, “solved all the problems with the more conventional options. It was at that point I decided I’d like to go back to university to study this theory some more, and I’ve never looked back since.” It was while doing postgraduate study at the University of Reading that he “finally found a philosophy professor who shared my philosophical convictions: Galen Strawson”.

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Asked about the objections often offered to panpsychism, Goff says he “always want[s] to emphasise that we shouldn’t be looking for the view we’d most like to be true, but the view that’s most likely to be true. And I do think there’s a good case for the probable truth of panpsychism as the best account of how consciousness fits into our scientific worldview…I also think that it has the potential to foster a better relationship to the environment…if you think a tree is a conscious organism of some kind, albeit a very alien one, then it has value in itself; chopping down a tree is an act of immediate moral significance.”

Matthew Reisz