Consciousness is said to be “one of the last
great mysteries for science”. It is at once the most familiar thing
in the world – I imagine you are having conscious experiences right
now – and the most difficult to explain. Oddly enough the great
successes of modern neuroscience only seem to make consciousness
itself harder to understand.
The central mystery goes back through thousands
of years of philosophy; it is that the universe seems to contain two
completely different kinds of thing. On the one hand are bodies and
brains – physical objects that we can touch and measure and
investigate: on the other are conscious experiences – private and
subjective feelings that we cannot get at directly. We can ask
people what they are experiencing, record their words, and measure
what happens in their brains, but somehow this doesn’t seem to
capture the “what it’s like” of subjective experience.
Right now for me the sky is a very faint pale
blue streaked with early morning wisps of delicate pink. But how can
science measure this? We can’t even tell whether you and I are
having the same experience when we both say we are seeing blue. My
pale blue might be your bright orange. This “what it’s like for me”,
these blue and pink experiences, are what philosophers call “qualia”;
the intrinsic properties of the experiences themselves. So the
mystery is this – how can a couple of pounds of squishy living
neurons inside a bony skull create qualia? How can electrical
signals in a brain give rise to a world experienced by me? No one
knows.
No one knows, but at least they are arguing
about it now. When I started my research, over thirty years ago, no
serious scientist would even admit to an interest in consciousness,
and I was very much on my own. I had had many strange experiences
and was obsessed with trying to understand them, but the science
simply wasn’t there to do the job. Then gradually I found I was in
the midst of a hot topic. Brain scanning and other advances in
neuroscience meant we could at last peek inside a living brain, but
how could we find consciousness there? The problem really got me
hooked, and so I gave up my university job to read everything I
could on the subject and write a textbook; a project that took me
several years, leaving me very well informed but even more baffled.
Everyone seemed to disagree. So I decided that I needed to ask the
experts what they really meant – face to face – and that is what I
did. I travelled the world talking to some of the worlds finest
thinkers and put together this book of our “conversations on
consciousness”.
King of the mystery is the young Australian
philosopher David Chalmers, instantly recognisable with his blue
jeans and long brown hair. I caught up with him in Tucson Arizona
where, for many years, he has organised the famous “Toward a Science
of Consciousness” conferences. He told me about his very first
conference in 1994, back in the days when consciousness was still a
taboo subject. He planned to give what he hoped would be a deep
philosophical lecture, prefaced by a few simple remarks. No one
remembers the difficult part but everyone remembers the beginning.
He said that scientists doing research on vision, memory, thinking
or emotions were just tackling the “easy problems”. Even if they
solved all those there would still be something else left to explain
– consciousness itself – and this he called the “Hard problem”.
The name stuck, and now Chalmers’s hard problem
has become something of a Holy Grail for consciousness studies.
Scientists and philosophers are falling over each other to become
the one who solves the hard problem. The trouble is, no one knows
how to set about solving it, or even what to look for.
At one extreme are those who think we need a
revolution in physics to solve it, such as the flamboyant Tucson
anaesthesiologist, Stuart Hameroff. “Every day” he told me “I put
patients to sleep and wake them up and it’s still incredible. You
wonder - where do they go?”. He has teamed up with the British
mathematician, Sir Roger Penrose, to argue that the brain is a
quantum computer and the conscious self depends on quantum effects
in the microtubules – tiny tubular structures inside every cell of
our bodies. They are convinced that this is the way forward, but no
one else I talked to shared their enthusiasm.
Far more common are the neuroscientists who
think that if we just get on with the “easy problems” we’ll
eventually solve the hard one. Pre-eminent amongst these is Francis Crick, who won the 1962 Nobel prize for discovering the
structure of DNA. After nearly half a century of biology, and at the
age of sixty, he changed tack completely – turning his attention
from the mystery of heredity to that of consciousness.
At the age of 88 and in failing health, he
invited me to his home in Southern California, and even rearranged
his chemotherapy so as to be at his sharpest for our discussion. And
that was very sharp indeed. Within minutes he had turned the tables
on me and was demanding that I come up with a crucial experiment.
When I tried my best he dismissed it out of hand. “I think all
that's nonsense” he said “because essentially it’s purely psychology
and you’re not talking about neurons.”
Crick had no time for the speculations of
psychologists or philosophers – all they do is argue, he said, and
they never make any discoveries. What we need to do is put the hard
problem aside and get on with studying the neural correlates of
consciousness; that is, measure what is going on inside the brain
when someone is having a conscious experience. In this light he, and
his long-time collaborator Christof Koch, were looking for the
consciousness neurons – the critical parts or processes in the brain
that are active when someone has a conscious experience.
He likens the hard problem to an ancient
conundrum – the nature of life itself. Back in the nineteenth
century, biologists were convinced they would find the special “life
force” or “Élan vital” that breathed life into plants and animals
and departed at their death. Of course no such force was ever found,
Crick himself contributing to its demise. The answer turned out to
be that when you understand how living things work you realise that
they don’t need any special force at all. Will it be like that for
consciousness?
The same analogy was used by Pat and Paul
Churchland, a remarkable couple who are both professors of
philosophy at the University of California, San Diego. They take a
very strong line on Chalmers and his hard problem. “His presumption
strikes me as ridiculous.” said Pat over bagels and coffee by their
living room fire “I don't see how you can tell, by looking at a
problem, how difficult it is. There are lots of examples where
people were convinced that one problem was unsolvable, while some
other problem was trivial, and they turned out to be wrong about
both.”
For the Churchlands, there is no separate
“mystery of consciousness”; when we really understand how the
brain’s visual system processes colour information then the problem
of qualia will be solved. We’ll know all we need to know to explain
the blueness of the blue sky I’m looking at now.
Finally, the most extreme view is given by
Tufts University professor, Daniel Dennett. He is probably the most
misunderstood philosopher alive, and I was determined to get to the
bottom of his revolutionary approach. His critics have dubbed him
“the devil”, which seems not to bother him at all. They regularly
joke that his famous book “Consciousness Explained” should be
renamed “Consciousness explained away” because he denies the
existence of qualia and says there is no such thing as
“consciousness itself”. Dennett believes that if we start from our
ordinary intuitions about consciousness then we are doomed to
failure because all those intuitions are completely wrong. For
example, you probably feel as though you are a little conscious self
somewhere inside your head, who is the subject of the stream of
experiences. This image is what Dennett calls the “Cartesian
Theatre” and it cannot possibly exist. The brain has no central
controller, no inner screen where the images could appear; and no
one inside to experience them. There is no magic process that turns
ordinary nerve activity into conscious experiences. We must, he told
me, throw out all these perfectly natural, but misguided ways of
thinking about consciousness. But how? Turning your intuitions
inside out is terribly hard, but if Dennett is right then most of
the others I spoke to are completely wrong. Quantum physics will not
help one jot, and no one will ever find Crick’s “consciousness
neurons”.
I would love to pop into the Tardis, jump
forward a few years, and see who turns out to be right. For now
consciousness looks set to remain one of our greatest mysteries.
