Soul Dust: the Magic of Consciousness By Nicholas Humphrey London: Quercus 2011 ISBN 978 1 84916 237 1 Nicholas Humphrey thinks that consciousness is a kind of illusion. He claims that when we have conscious sensory experiences, it seems to us that we are aware of certain "phenomenal" properties like colours, smells, sounds, when in reality there are no such things. In fact, there cannot be any such things, since phenomenal properties are impossible. Something in our brains causes us to have experiences which represent "extraordinary otherworldly properties". The whole of conscious experience seems to us like something "magical"; hence the subtitle of the book. Humphrey's model for this is the impossible Penrose triangle, and the ingenious object which Richard Gregory invented to create a three-dimensional version of the Penrose illusion. Gregory's object is real enough. But the illusion it presents is of something impossible: magic! Likewise, Humphrey claims, something real in our brains produces in us the illusion of magical phenomenal properties or "qualia". "Consciousness" he says "is a magical mystery show that you lay on for yourself." As his analogy with the Penrose triangle makes clear, Humphrey's point is not just the familiar one that the production of consciousness by the brain is mysterious or "magical". It is also that consciousness seems magical to those who have experiences: "from the subject's point of view, consciousness appears to be a gateway to a transcendental world of as-if entities". When we have a conscious experience, he claims, it seems to us that we are "on a separate plane of existence from the physical world". Is this right? Does the taste of toothpaste or the smell of coffee seem impossible or magical? Impossible compared to what? Isn't that what toothpaste and coffee are supposed to taste and smell like? Does tasting toothpaste seem to put us in touch with "extraordinary otherworldly properties"? Surely not: the properties of toothpaste and coffee seem as normal as toothpaste and coffee themselves. If the water I drank were turned into wine, if the toothpaste tube disappeared when I touched it, if the smell of coffee were created by clicking my fingers... that would seem magical or otherworldly. But what is the reason for saying that ordinary, everyday experience seems magical? There are actually two very different issues here. One is whether it is mysterious, unintelligible or "magical" that consciousness could be produced by the brain. Many will agree with Humphrey here that consciousness is a mystery in this sense. But it is quite another thing to say that consciousness itself seems mysterious. Consciousness is the product of the brain; and it is mysterious which processes produce it. But just because the underlying process seems mysterious, this does not mean the product should. I still can't help finding wireless printing an amazing, almost mysterious, process. But this does not mean that the product of this process – the document which emerges – seems mysterious. Humphrey's analogy with the Penrose triangle fails, because most conscious experience does not seem impossible or magical at all. Humphrey has a nice range of quotations from poets and others describing the wonders of sensory experience; but finding experience wonderful is not the same as finding it magical or mysterious. A perfectly ordinary thing like a glass of cold water can sometimes seem the most wonderful thing in the world, without it seeming to put us on a "separate plane of existence". However, it's not essential to the idea that consciousness is an illusion that it should seem impossible. It could just be a perfectly ordinary illusion: that is, a representation of something which is not so. Since Galileo, many have argued that our experience of colour is this kind of illusion: colours are not really in the objects where they seem to be, but are really some kind of construct of our mind or brain in response to the intrinsically colourless objects (Locke called colours "secondary qualities"). Humphrey thinks something like this too: he claims that an experience of (say) a red tomato is really your "observation" of your own intra-cerebral reaction to an external stimulus. The idea of "observation" here can seem paradoxical – who or what is doing the observing? Does this observation involve further phenomenal episodes? Similar questions arise with the claim that consciousness merely seems to involve phenomenal properties, when the idea of a phenomenal property is normally introduced precisely to describe how things seem. How many seemings are going on, and how are they all related? In philosophy, the adjective "phenomenal" means "pertaining to appearances". If we go along with this traditional use of the word, then there are many more phenomenal properties than the ones Humphrey considers. Like many philosophers, Humphrey restricts his study of consciousness to sensation, and does not consider the phenomenal properties of conscious thought, imagination or memory. And within sensory experience, he limits himself to what Locke called secondary properties (colours, tastes etc.). Yet conscious visual experience presents many other properties: for example, the geometrical properties of the apparent objects of experience. The tomato seems round as well as red. Is the roundness too an apparently magical property? Surely not: things in the external world can be (more or less) round. But if so, then not everything presented by conscious experience need be illusory. The second part of Humphrey's wide-ranging book is concerned with how consciousness might have evolved. His hypothesis is that consciousness makes life more interesting for us, and for this reason conscious creatures would have had an advantage over their nonconscious competitors, as they actively struggle to pursue desirable experiences and to produce more conscious creatures on the way. Like many claims in evolutionary psychology, this is largely speculation (as Humphrey willingly admits) since we have no evidence of how things were, psychologically, at the time when the supposed competition for survival was taking place. Nonetheless, Humphrey's general claim that much of what matters to us involves phenomenal consciousness is very plausible. What is harder to see is how this would work when "phenomenal consciousness" is restricted only to the properties of sensation which he considers. The evolutionary function of consciousness, he claims, is to "enourage you to ... take an interest in things that otherwise would not interest you, to mind about things you otherwise would not mind about, to set yourself goals you would not otherwise set". Phenomenal experiences "change your worldview so as to change the direction of your life". The problem here is that without phenomenal consciousness we would not (literally) mind or care about anything at all, we would not set ourselves any goals, and we would not even have a worldview. Plants and molluscs do not have worldviews, interests and goals. So it's hard to make good sense of the idea that there was once competition between organisms with worldviews, goals and interests, and organisms with all this, plus phenomenal consciousness. A more realistic comparison (which Humphrey himself would have a lot to say about) is between the forms of consciousness found in non-human animals, and the sophisticated conscious lives of humans. But what humans have and these other creatures don't is not just more sensation, but rather the other mental capacities Humphrey mentions: goals, interests and a worldview (all of which are, for us, aspects of our conscious lives). Humphrey is absolutely right that our phenomenal consciousness makes life worth living; but only if "phenomenal consciousness" is understood broadly enough to include all of these other mental states, and not just the "qualia" of sensation. Tim Crane is Knightbridge Professor of Philosophy in the University of Cambridge