Why do we experience consciousness?
Tim Crane
This year marks the thirtieth anniversary of the publication of David Chalmers’s book The Conscious Mind. Chalmers – only thirty years old at the time – was trained as a mathematician in his home city, Adelaide, and had studied philosophy in Oxford and Indiana before becoming a professor at the University of California. The book made a huge impact, breathing new life into the somewhat moribund scientific study of consciousness and helping to put the not-so-moribund philosophy of consciousness on the agenda of scientists. According to Google Scholar, Chalmers’s book has been cited more than 16,000 times, and it was the first step on its author’s path to philosophical stardom. Love it or loathe it, the study of consciousness would not be what it is today without The Conscious Mind.
One of its most influential aspects is its conception of the problem of consciousness itself. Chalmers distinguished between “easy” questions – “How does the brain process environmental stimulation? How does it integrate information? How do we produce reports on internal states?” – and the “hard” question: “Why is all this processing accompanied by an experienced inner life?” His point is that it is one thing to explain how the mechanisms of experience work, but a further thing to explain why the operations of these mechanisms give rise to consciousness: why do their operations feel like anything at all? In the early 1990s, for example, Francis Crick and the neuroscientist Christof Koch proposed that the “neural correlate” of consciousness was 40 Hz neural oscillations in the cerebral cortex. Chalmers’s challenge is: why should 40 Hz oscillations feel like anything at all? This question is one way of posing the “hard problem”.
Michael Pollan’s new book is an engaging and insightful account of the hard problem of consciousness and today’s attempts to solve it. Pollan is particularly known for his writings on food – his In Defence of Food (2008) contains the memorable and wise advice: “Eat food. Not too much. Mostly plants”. He is neither a philosopher nor a neuroscientist, and accordingly A World Appears is lucid and intelligible to non-specialists. Pollan approaches the problem as an outsider, interviewing many of the leading scientists working on consciousness, as well as some philosophers, and interspersing these interviews with his own speculations.
The author takes evident pleasure in the “deliciously gladiatorial” nature of the consciousness debate, his interviews emphasizing the personalities involved as well as their appearances. Michael Levin “has a thick, Kennedyesque mop of dark-brown hair, piercing pale-blue eyes, a full beard, and a slightly elfin aspect”, Anil Seth is a “tall, lanky man with a clean-shaven head”. But Pollan is not a slavish science fanboy. He asks the scientists pertinent questions and often raises cogent objections to their answers. The book documents his swings and shifts of opinion on the problem of consciousness, sometimes in reaction to these conversations with the scientists.
The main body of the book is divided into four sections, “sentience”, “feeling”, “thought” and “self”. “Sentience” is his word for the most basic form of consciousness. The philosopher Evan Thompson nicely describes it as “the feeling of being alive”. Rather confusingly, Pollan reserves “feeling” mostly for emotions; he interviews Antonio Damasio on his well-known views about the centrality of emotions to thought and reason. He also discusses AI and machine consciousness.
The classification of kinds of consciousness here is somewhat arbitrary – the terms “sentience” and “feeling” are not precise enough in their ordinary meanings to bear the distinction Pollan is making. But it doesn’t really matter, since his aim is clear enough: to build up from the simpler forms of consciousness, through emotion and sensation, to thought and finally to self-consciousness.
The book begins with a discussion of the possibility of plant sentience. Presumably, the idea is to plot the limits of consciousness across all species. And, of course, plants do track sources of light and nutrients, and some of them even move. But the ideas discussed with the researchers here – that plants sleep, or can be anaesthetized, or feel pain – are far from anything resembling scientific orthodoxy, so it is rather disorientating to begin a book on consciousness by taking them so seriously. It would have been better, perhaps, to begin with the assumption that plants are not conscious, then ask what we and other animals have that they lack. Neurons would be a start.
When it comes to the supposed possibility of AI consciousness, Pollan is refreshingly assertive and sceptical. The claim that brains are computers is “a metaphor parading as fact”, and he comes down strongly in favour of those such as Seth and Ned Block, who hold that consciousness is fundamentally a biological rather than a computational phenomenon: “It seems to me that only living, mortal systems – those that can die, in other words – have true goals and intentions, survival and reproduction being the most universal. To the extent that a thermostat has a goal, it is a secondhand one: the one we have given it”.
The Thought section contains some of the best material in the book. It is concerned largely with the difficulty of describing something that is obvious to us: the “stream” of conscious thinking. When we try to describe what we are currently thinking, we risk imposing an order on the thought that wasn’t there originally. Thought seems full of material, and “pinning it down” in words can distort it. Pollan visits the psychologist Russell Hurlburt, who pioneered the practice of “descriptive experience sampling”: subjects are connected to a beeper that goes off at random, and they must then write down as best they can what they are thinking at that moment. Hurlburt’s method did not catch on, and Pollan finds it frustrating and Hurlburt’s approach somewhat irritating. But his serious attempts to try to follow this procedure, and his general observations on the stream of consciousness, are insightful.
When it comes to the massive and baffling topic of the self, Pollan treats the topic in an indirect way, looking at experiences of selflessness in meditation and other contexts. In this way, he locates an apparent paradox: “Why do we cling to the idea of a self, placing great value on self-confidence and self-esteem, while simultaneously spending so much effort on self-transcendence, whether through meditation or psychedelics or experiences of art, awe and flow?” What is needed here is a better understanding of what it means for these experiences to be “selfless”, while recognizing with Pollan that “some of the most powerful experiences in life hinge on the dissolution of the self and the broad horizons of meaning that open only after it has been chased from the scene”.
Pollan draws no major conclusions, and the book ends with him rather dejectedly explaining to Koch that after five years “wandering in the exitless labyrinth of consciousness”, he felt he knew less than he did when he started. Koch’s response is Socratic: “That’s progress!”.
Pollan is a superb writer. His evocation of the experience of taking hallucinogenic mushrooms is a tour de force of phenomenological reflection, as are his attempts to pin down what is currently going on in his stream of consciousness. And then, dropped among the descriptions of his visits to scientists are perfect observations such as this: “for the first time that season, the air had that metallic tang it acquires as soon as the weather gets too cold for it to carry the scents of living things”. You know exactly what he means.
There are some things missing, and the book is accordingly a little unbalanced. There is no serious discussion of the global workspace theory of Bernard Baars, and rather too much about plants. The presentation of the scientific views that Pollan does discuss is for the most part accurate, though there are a few baffling comments. For example, he reports without criticism the view of the Canadian psychologist Kalina Christoff Hadjiilieva that psychology has “neglected the unconscious”, while having stated some pages earlier that most of what the science of the mind studies goes on without consciousness. What Christoff Hadjiileva may have had in mind was the unconscious as conceived by Freudian psychoanalysis, which is certainly out of favour in mainstream cognitive psychology. But Freud has no patent on the concept of the unconscious, and Pollan makes no attempt here to distinguish the Freudian unconscious from the unconscious as conceived by other theorists.
Another eccentricity is the attention paid to psychedelics and their mind- altering properties. There is no question that mushrooms and other psychedelics broaden the range of available conscious experiences; but reflection on the ordinary conscious experiences of seeing, hearing or feeling pain is enough to generate the mystery of consciousness. (Not having taken psychedelics myself, I concede that I might be missing something.)
But these are minor complaints – the book as a whole is engaging, readable and informative. As a philosopher, I naturally felt that philosophy did not get enough of a look-in. Many philosophical theories of consciousness have been proposed in the past few centuries. Some philosophers think that the hard problem requires a radical metaphysical shift – a shift in our conception of reality – towards a rejection of materialism, or to Descartes’s dualism, or to the lunatic fringe of panpsychism, the view that all matter experiences consciousness of a primitive kind. Pollan may reply that he is only concerned with scientific approaches to consciousness, but given the level of wild speculation in some of the theories he does consider, it’s obvious that the scientists are up to their necks in philosophy here.
Pollan only really considers one philosophical approach that rejects the whole hard-problem framework – Evan Thompson’s, from his recent book The Blind Spot. Thompson and his co-authors, the astrophysicist Adam Frank and the theoretical physicist Marcelo Gleiser, propose that the problem of consciousness is insoluble using familiar scientific methods, and that this requires that we rethink science. But Pollan himself never really questions Chalmers’s framing of the problem of consciousness.
Other approaches are available. For example, we could try to step back and look at the way the hard problem is constructed. Sometimes, when reading scientific attempts to solve this problem, one wonders whether the target has been set up in such a way as to render it unreachable. Has the bar for explaining consciousness been set too high by Chalmers and his followers? At one point, Pollan poses Chalmers’s question to the biologist Michael Levin: “At best, third-person science may identify the neural correlates of consciousness. But it’s never going to tell us what it is actually like to be inside the head of another being, human or otherwise”. Levin replies that you would only learn this “by experiencing it yourself”.
This is surely correct, and it provides a way of dissolving one aspect of the hard problem. You can’t get to know what an experience is like “from the inside” by learning a scientific theory of that experience. But rather than reacting to this by proposing that we rethink science, we should come to terms with the fact that there are some things you can only know by experiencing them. Einstein is supposed to have said that “science cannot give you the taste of chicken soup”. But this obvious fact is not a shortcoming of science. Instead, it highlights science’s aim: to explain and describe and predict things, not to give you experiences you would not otherwise have had.
Another formulation of the problem relies on the idea that, when faced with a proposed account of consciousness, it seems that you can always keep asking the question: “but even if things are the way this account says, why should they be accompanied by consciousness?”. This is analogous to a famous argument in ethics, G. E. Moore’s “open question argument”. Moore argued that any analysis of goodness in terms of some natural property (such as happiness) could be refuted by simply posing the question: “but is that really good?” Similarly, those in thrall to the hard problem tend to ask, when faced with any account of the mechanisms of consciousness: “but couldn’t that exist without consciousness?”
The only way to reject this all-purpose sledgehammer of an argument is to look closely at what it is assuming. One assumption is that an explanation of consciousness should create a logical or necessary connection between the explaining mechanisms and consciousness itself. The hard problem needs this assumption because it is the only way that it could be relevant to ask, when presented with a candidate mechanism for consciousness, “but why should that produce consciousness?”. Without the assumption of a logical connection, this question collapses into: “I don’t believe your theory”.
Chalmers has never really questioned the basic assumptions behind his problem. As Pollan says, he is still the “devoted guardian of the hard problem … he now serves as a kind of conscience, or superego, passing judgement on any who would venture a solution to The Problem”. Pollan adds wryly that by now Chalmers “must be deeply invested in the hardness of the hard problem”, showing a flicker of resistance to Chalmers’s vision of things. Perhaps this investment is a bubble, and the philosophical “stock” of the hard problem is massively overvalued. To bring about a crash in the market, we need to look more sceptically at the assumptions of this problem – the idea that science should be able to give you the taste of chicken soup, or the idea that there has to be a logical or necessary connection between matter and consciousness if we are going to understand how one gives rise to the other.
This is not to say that all contemporary attempts to explain consciousness are misguided, only that they are perhaps best conceived not as attempts to solve this unsolvable problem. There are different models or paradigms of scientific or technological achievement. One kind is the moon landing: there was one thing they had to do, get someone on the moon, and they did it. Another is the search for a cure for cancer: here there is not one thing to do, but many. There are many kinds of cancer, and progress has been made in curing or treating many of them. But it is highly unlikely that we will get to the point of saying, “now we have cured all cancer”. Theories of consciousness should perhaps be construed along the lines of the second model rather than the first. There may then be small grains of truth contained in many of the theories discussed in Michael Pollan’s fine book.
Tim Crane is Professor of Philosophy at the Central European University in Vienna, and the Director of Research of the Austrian Science Fund’s Cluster of Excellence, Knowledge in Crisis.
You can also find this review for the Times Literary Supplement on its website.