The American writer Tom Wolfe has warned that: "The opening of the 21st century may see man proclaim the death of the soul." Wolfe was echoing Nietzsche's proclamation of the "death of God" a century ago, and suggesting that we are entering an era in which science would attempt a total explanation of the human condition with no place for a spiritual dimension. The argument is that humans are essentially super-sophisticated soft machines, an accident of genetics and natural selection, controlled by a mind created from complex electrochemical processes in the brain.
How close are we to this big picture? The mapping of the human genome is nearing completion, offering a giant leap forward in understanding
our biological geography and history. But there are many knotty problems still to unravel. Across the world scientists are seeking to answer the biggest enigma of all: the nature of human consciousness.
What exactly is this mysterious stuff called consciousness by which we know the world and ourselves? It cannot be seen, held, touched or measured. It is the "I" that experiences the world out there in all its complexity and turns the evidence of the senses into the stuff of self - a private universe of memories, fears, hopes, anxieties, dreams and more.
In ancient Greece, Plato was convinced the location of this "self" was in the head because it was closest in shape to the ideal geometrical sphere. By medieval times most people believed that the brain was the seat of our minds, but had no idea why. Religious prohibitions on anatomical research meant it was left to the philosophers to reason things out.
The French philosopher Rene Descartes crystallised the question in the 17th century when he wrote: "I know that I exist. The question is, what is the "I" that I know?" His solution was "Cogito, ergo sum" (I think, therefore I am). Our consciousness, he suggested, was the only evidence that we actually exist. But it existed separately from the body. Despite the scientific revelations since then, the idea of a soul has had an enduring currency.
The mainstream of modern thinking roots it all back in the biological. The controversial American cognitive scientist Professor Stephen Pinker argues in his bestseller, How The Mind Works, that our minds are essentially computers that shape human nature and are themselves shaped by natural selection. There's no place in this philosophy for God or the soul. And, by extension, precious little for the notion of the individual.
The topic of consciousness has been popularised in Britain by Professor Susan Greenfield, the charismatic director of the Royal Institution. She says: "Consciousness is the essence of the individual. It really represents the final frontier for science." A brain specialist with professorships in Oxford and London, Greenfield roots her ideas about consciousness in neuroscience and asks: " How do our personalities, our states of consciousness, derive from a grey mass of tissue with the consistency of a soft boiled egg?"
From the outside, this mushy mass tells us nothing about the individual personality. But it is inconceivably complex. Each individual's brain has hundreds of billions of brain cells - or neurons; the constantly shifting synaptic connections between them would take billions of years to count.
Greenfield explains the connection between brain and mind by suggesting that when an event occurs - we see a red rose, taste an apple or hear laughter - our brains respond and create our consciousness of this stimulus by triggering an incredibly complex configuration of electrical impulses and chemical interactions. She uses the analogy of an infinitely vast symphony orchestra coming together to work in unique arrangements for every type of event to create a region of consciousness. Observation suggests utterly disparate parts of the brain are involved.
But the scientific spectrum is wide. One of Britain's greatest mathematicians and theoretical physicists, Professor Sir Roger Penrose, has very different ideas. He says: "Human consciousness is the deepest question of all. Who are we? What are we doing here? What is existence about? What lies at the heart of it?"
He has written three challenging books explaining why theoretical physics might yield answers to the enigma of consciousness and doubts if current research will because it is not looking in the right place. Penrose believes that the essence of mind is likely to be found only when we solve one of the fundamental questions of physics: what can bridge the gap between the behaviour of the smallest known particles in the universe (the sub-atomic world of quantum physics) and things on a cosmic scale (the bewildering world of black holes, singularities and relativity). His answer is that our minds somehow provide this missing piece of the jigsaw puzzle -- that consciousness may be some form of quantum activity.
The trouble is proving it. Science just isn't equipped to test his theories. For centuries, science had no tools to investigate something as evanescent as consciousness and, until recently, the issue was left to theologians, philosophers and psychologists. But now new technologies enable neuroscientists to probe the behaviour of our brains as never before - sophisticated brain scanning machines utilizing fMRI (functional magnetic resonance imaging) or PET (positron-emission tomography). They make it possible to see neural events as they occur, allowing scientists to watch parts of the brain light up in response to a joke or flinch
The mechanistic view of the mind as a super-sophisticated computer has prompted intensive attempts to create computer neural networks that have thoughts and feelings. But Penrose and most neuroscientists see this as a technological blind alley. Susan Greenfield says: "The idea is ridiculous. Consciousness entails an interaction between the body and the brain trafficking a myriad of chemicals between the two. To reproduce that, you would have to build a body with a whole range of chemicals and the three dimensionality of the brain would have to be preserved to the very last connection."
But philosophers suspect the whole venture of trying to understand consciousness may be destined to fail. Galen Strawson, for instance, a fellow of Jesus College Oxford says: "There are a lot of things that I think science will not be able to answer and I'm inclined to think that consciousness is something we are just going to have to accept; that matter, as it's arranged in the brain, produces consciousness."
The benefits of understanding consciousness could bring a breakthrough in understanding and controlling conditions such as Alzheimer's and Parkinson's and in gaining a deeper understanding of persistent vegetative states. It could also lead to more effective computers and robots.
But if we do finally explain consciousness, then Wolfe's fears may also be founded. The great
American naturalist Edward O Wilson sums up the hopes and fears of this search. In his book
On Human Nature he wrote: "If the brain is a machine of ten billion nerve cells and the mind can, somehow, be explained as the summed
activity of a finite number of chemical and electrical reactions, boundaries limit the human
prospect. We are biological and our souls
cannot fly free."