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鈥淣OBODY expects the Spanish Inquisition,鈥� says our philosopher hero, Miranda Sharpe, to her empty-headed cat. Indeed they don鈥檛. And nobody expects to read an exciting crime thriller that is set in the world of cognitive science, peopled by real philosophers who care about the mysteries of existence, and that claims to present a new theory of consciousness.

The author, Dan Lloyd, a neurophilosopher from Trinity College in Hartford, Connecticut, has burst onto the consciousness scene with a book that is both a gripping story and an intellectual challenge. He even appears in his own plot, portraying himself (or his namesake) as a polite, if dull, middle-aged cognitive scientist who creates the best-ever website on consciousness.

The story begins one day at 6 am when graduate student Miranda slips unnoticed into her professor鈥檚 office and finds, to her horror, that the gruesome Max Grue is slumped over his keyboard. Asleep? Sick? Dead? She grabs what she has come for, a bright red folder labelled 鈥淐onsciousness鈥�, and runs.

The folder contains many surprises, as does Miranda鈥檚 quest to find out what has happened to Max 鈥� not least because to do so she must solve the mystery of consciousness. But perhaps the most surprising thing of all is Miranda鈥檚 obsession with what she calls 鈥渢he thrill of phenomenology鈥�.

It has to be said that not many people find phenomenology thrilling. This daunting philosophical tradition is based on the work of German philosopher Edmund Husserl (1859-1938), who advocated exploring consciousness by suspending judgement and looking directly into immediate experience. Phenomenology has recently become very trendy in consciousness studies, perhaps because it offers the hope of reconciling private, conscious experiences with the study of the brain. But the field is notorious for its impenetrable language and slippery concepts.

Yet Miranda loves it. One morning, finding herself alone in charge of Max鈥檚 class on 鈥淭he mystery of consciousness鈥� she is confronted by a Barbie-faced sophomore who complains 鈥淚 don鈥檛 get any of this at all鈥� 鈥� an understandable reaction from a student encountering Husserl.

Miranda rises to the challenge. She explains to the class why appearance is reality, why meaning takes time, and why the mind is a text. She even explains that in this context 鈥渟uperposition鈥� has nothing to do with quantum physics, but refers to Husserl鈥檚 idea that conscious experience is always heaped up with meanings 鈥� every moment of awareness is a pile of interpretations all in superposition. A single state of mind is layered with harmonics of meaning 鈥� yet somehow remains one experience.

You might dismiss all this as wordy waffle, and the book along with it. But there are good reasons not to. One is that Miranda really does understand why consciousness is such a mystery. Another is that Max, and by implication Lloyd, claims to have built a scientific theory that bridges the gulf between neuroscience and phenomenology.

So, first to the mystery. At the start of the 21st century, there are hundreds of books on consciousness and dozens of writers who claim to have solved it. One of the most frustrating things is how few of them appreciate just how deep the mystery is. Daniel Dennett, a philosopher at Tufts University in Massachusetts and author of Consciousness Explained, defines a mystery as something 鈥渢hat people don鈥檛 know how to think about 鈥� yet鈥�. He calls consciousness 鈥渏ust about the last surviving mystery鈥�.

The trouble lies with subjectivity, or 鈥渨hat it is like鈥� being me now. For example, I am right now having the experience of sitting in this room, with all its many sights, sounds and feels. My experience seems to be private, fleeting, ungraspable and utterly undeniable, and this is what we mean by consciousness. But how can this subjective experience relate to the objective world around me and to the physical brain inside my head? Real, physical things like rooms and brains seem to be of a completely different order from subjective, conscious experiences.

We face what Australian philosopher David Chalmers of the University of Arizona calls the 鈥渉ard problem鈥� 鈥� the impossibility of seeing how the activity of brain cells can possibly give rise to subjective experience. In spite of dramatic developments in neuroscience, there is still this fathomless abyss between the objective and subjective worlds. We can study the conscious experiences of 鈥渕indspace鈥� and the neural events of 鈥渂rainspace鈥�, but we never seem able to map one onto the other.

Half-baked theories of the 鈥渃onsciousness is a fifth dimension鈥� or 鈥渃onsciousness is a spiritual force鈥� variety miss this point completely. But so do the many scientific theories that locate consciousness in one part of the brain, equate it with a particular pattern of neural firing or reduce it to quantum levels inside minuscule cellular structures. In every case the mystery remains because it is impossible to see why that particular process or this particular brain area is conscious while all the rest are not. In fact, just about every theory we have fails utterly in this way and leaves the fundamental mystery untouched.

So it is refreshing to find that Miranda does agonise over the problem. When Gordon, the neural-network-building nerd, makes the banal observation, 鈥淚t鈥檚 all neurons. That鈥檚 all,鈥� Miranda is quick to challenge him. How can a neuron be conscious? How can a physical piece of brain be a private experience? 鈥淲hat is it about neurons that makes them the medium of superposition?鈥� she asks. 鈥淲hat is it about the neurons that makes seeing and smelling different?鈥� Gordon cannot answer, but it turns out that before Miranda found Max slumped in his office, the two of them had been secretly sketching out what a viable theory of consciousness would need to do.

They explain their aim like this: it may be true that 鈥渋t鈥檚 all neurons鈥�, but that statement is opaque because no one can understand how it could be true. The ultimate theory of consciousness must be a transparent theory that makes it obvious how consciousness can be the activity of neurons. In such a theory, every description in 鈥渕indspace鈥� will have an equivalent description in 鈥渂rainspace鈥�. So Max and Miranda set about using phenomenology to map out the nature of conscious experiences and then try to fit this with neuroscience 鈥� eventually creating the theory on which the plot depends.

Thought experiments

So how well does this theory fare? Lloyd describes the act of writing a novel as 鈥渢he most thorough thought experiment鈥�, implying that the story might help to reveal the implications of his theory. Yet the novel itself proves insufficient to explain what the theory is. So Lloyd adds over a hundred pages of helpful appendix to do the job. Here we are given a tutorial on some difficult concepts 鈥� recurrent neural networks, high-resolution brain scanning, multidimensional scaling and the practice of phenomenology, all of which are necessary for understanding his theory.

Much of the explanation deals with the experience of time 鈥� a favourite preoccupation of phenomenology. Rather than assuming that consciousness consists of a sequence of distinct, separate moments happening one after the other, Husserl stressed that every 鈥渘ow鈥� carries within itself the shadow of what is just past and the expectation of what comes next. So not only is conscious experience always heaped up with superimposed meanings, but each 鈥渘ow鈥� is a confluence of retention, presence and protention. This is Husserl鈥檚 famous tripartite structure of time, and it is this phenomenological 鈥渘ow鈥� that Lloyd wants to describe in brain terms. He will then have achieved his goal of mapping the mind to the brain and thus his 鈥渢ransparent theory of consciousness鈥�.

The task, then, is to find a way of describing what the brain does that fits phenomenology. Lloyd claims that conventional theories cannot do the job, but that simple, recurrent neural networks can. Neural networks are computer simulations of the way real brains might work. Typically, they consist of several layers of highly interconnected units, each of which represents a neuron: an input layer, an output layer and some hidden layers in between. The strength of the connections between the units changes with new inputs, and the state of the whole complicated network determines what its output will be. These artificial neural networks have been highly influential in cognitive science.

In 1990, Jeffrey Elman, professor of cognitive science at the University of California, San Diego, proposed a new sort of 鈥渞ecurrent network鈥� that has an extra 鈥渃ontext layer鈥�. This copies the most recent state of a hidden layer and then presents it alongside the next input. So, in effect, the network enfolds both past and present information. If brains are like this, claims Lloyd, a description of how they work might just match the phenomenological description of 鈥渘ow鈥�.

To find out, Lloyd measures the activity of such networks, but their behaviour is so complicated that it can only be described in terms of a vast, multidimensional space. To clarify things he uses a mathematical technique known as multidimensional scaling. This reduces the mathematical space to just two or three dimensions, making it much easier to understand what is going on.

Playing with multidimensional spaces like these provides fun for the novel. Through her humble laptop, Miranda is drawn into the fictional Dan Lloyd鈥檚 鈥渂est-ever鈥� consciousness website, the Labyrinth of Cognition, swooping through a virtual world of spaces of the mind. 鈥淭his is what I am,鈥� she cries, 鈥淢iranda Sharpe, an ever-shifting pattern in the dark.鈥� She falls into multiple states of consciousness until she becomes 鈥渢he brain from the brain鈥檚 own point of view.鈥� This is where brain map and phenomenology finally fit together. This is where 鈥渂rainspace is also mindspace鈥�.

It鈥檚 a fun story, but does the theory really apply to the brain? To find out, Lloyd would need to apply the same mathematical analysis to data from human brains 鈥� and he would need lots of data. Fortunately this is available. Researchers have been depositing vast amounts of data from brain-scanning experiments at the fMRI Data Center at Dartmouth College in Hanover, New Hampshire, and this is what Lloyd used. The artificial net Lloyd had already created was complicated enough, but this meant another leap in complexity 鈥� he compares it to swapping a pair of binoculars for the Hubble Space Telescope. He took the masses of data from functional magnetic resonance imaging (fMRI), applied the same multidimensional scaling techniques, and hoped that Husserl鈥檚 phenomenology would predict what he found.

Flowing with time

Simplifying drastically, the argument goes like this. According to phenomenology, 鈥渢emporality鈥� is in everything we experience. So if it could be observed in the fMRI data it should be seen in a wide variety of tasks and across many regions of the brain. Phenomenology also describes experience as in continuous flux and temporality as monotonic 鈥� that is, it always goes in one direction. So change in the brain should also be seen always going in one direction. Put more concretely, a person鈥檚 fMRI data should show that as their brain states change, the difference between successive ones should increase continuously over time rather than the brain returning again and again to a similar state. This is, indeed, what Lloyd found. The brains, he said, were 鈥渇lowing with time鈥�.

Success? Maybe not. David Rose, a psychologist at the University of Surrey, UK, says it鈥檚 鈥渁 nice idea but it鈥檚 not going to work in practice鈥�. The fMRI data come from changes in blood flow that have a resolution of a few seconds and so are much too slow to track the phenomenological structure of time. As Rose explains, 鈥淟loyd has not shown the 鈥榯ripartite鈥� nature of phenomenality reflected in the brain 鈥� he has just shown that taking an instant in the brain鈥檚 flow of activity enables you to predict the brain鈥檚 state 2 or 3 seconds into the future or the past 鈥� a trivial point to make.鈥�

鈥淪cientifically it鈥檚 nonsense,鈥� says Chris Frith of the Functional Imaging Laboratory at London鈥檚 Institute of Neurology, because Lloyd has not done the necessary controls. 鈥淗e has shown that the conscious person has a brain with certain temporal properties, but he hasn鈥檛 shown that an unconscious person has a brain that doesn鈥檛 have these temporal properties.鈥� Without such a comparison, he says, we can draw no conclusions about consciousness.

For John McCrone, author of a book on consciousness called Going Inside, the ideas are not wrong, just vague and naive. 鈥淭he way Lloyd uses multidimensional scaling may be new and interesting, but I don鈥檛 think it confirms Husserl鈥檚 phenomenology any more than many other ideas.鈥�

This is the crunch. Lloyd may appear to have achieved a scientific success, making a prediction from his theory and confirming it with real data, but this same prediction could have been made in countless other ways without recourse to phenomenology. In essence Lloyd claims a symmetry between mind and brain 鈥� that you can鈥檛 step in the same stream of consciousness twice, and you can鈥檛 have exactly the same brain twice.

But surely these statements are obvious. On the mind side, ordinary introspection is enough to reveal this simple truth. On the brain side, the notion of continuous change is inherent in everything we know about this real, live, wet and growing organ. Its synapses are always changing and its tiny dendrites are always slightly growing or shrinking. Change in brains really is one-way. So Lloyd鈥檚 findings are not surprising.

Lloyd鈥檚 fictitious philosophers are after a transparent theory. 鈥淚t鈥檒l be about neurons,鈥� explains Miranda, 鈥渂ut once we get it, you鈥檒l be able to interpret the neurons as conscious states.鈥� If Lloyd鈥檚 theory does this, it should be obvious how the ever-changing brain gives rise to ever-changing experience. Yet it isn鈥檛. The transparent theory is as far off as ever.

Could it be a step in the right direction? Philosophers such as Dennett and Patricia Churchland of the University of California at San Diego believe that once we really understand the brain there will be no 鈥渕ystery of consciousness鈥� left over. Lloyd鈥檚 discoveries may be a useful step toward such a theory. But others disagree. For Chalmers, all this detailed study of the workings of the brain is part of the 鈥渆asy problems鈥� and does not touch on the real mystery of consciousness 鈥� the 鈥渉ard problem鈥� of why there is experience at all.

Whichever side you are on, Radiant Cool is fun, and philosophers and neuroscientists will love the jokes and allusions. There are flitting bats and brains in vats. There are 鈥渞eally awful鈥� simulations that, like the real world, appear convincing. And there is a terrifying brain machine that produces 鈥渂lindsight鈥� to order. With one zap the helpless, strapped-in victim claims to be blind, yet she can still correctly guess what is in front of her.

If the in-jokes pass you by, don鈥檛 worry. This is a terrific story and a great read. Enjoy it, but don鈥檛 expect that by the end you will understand the mystery of consciousness.