WHY ARE WE HERE? Could it be that life, perhaps even consciousness, is writ large into the laws of physics? Or is life just a fluke, the chance after-effect of a world that simply happens to exist - an accidental universe, so to speak?Successive religions have tried for millennia to explain existence by invoking the direct or indirect actions of a single deity or panoply of divine beings. Now a small but growing band of indefatigable scientists are trying their hand at fathoming the hitherto unfathomable.

Few are better equipped for the job than Paul Davies, the internationally acclaimed physicist and deepest of thinkers. He has long been puzzled by the universe's "bio-friendliness"; in other words, the laws of physics, like Goldilocks' porridge, seem "just right" for life. By life he doesn't mean Homo sapiens per se, but life in a general sense. This is just as well because Cambridge scientist Stephen Hawking once said: "The human race is just a chemical scum on a moderate-sized planet."

Davies is reluctant to dismiss life so readily. As far as he's concerned, science might never really get a fix on the grand cosmic blueprint (assuming there is one, of course) unless life and consciousness are adequately accounted for.Taking life, mind and purpose seriously, as he puts it, Davies writes: "I cannot accept these features as a package of marvels which just happen to be, which exist reasonlessly. It seems to me that there is a genuine scheme of things - the universe is about something."

At the same time, he is "uneasy about dumping the whole set of problems in the lap of an arbitrary god, or abandoning all further thought and declaring existence ultimately to be a mystery".

Religious believers worship such mysteries, or at least are used to being saddled with them, while atheistic scientists seem happy enough to write off the whole shebang as a series of coincidences and extraordinary but otherwise potentially explicable evolutionary accidents that merit no further thought or scrutiny.

Davies finds such approaches unsatisfactory. Why, for example, was this universe created and not another? (Other universes may exist - leaving ours as a self-contained region in a much larger multiverse - but these other worlds would be inaccessible.) What is the purpose of life - indeed is there one? And the biggest conundrum of all: why does the universe exist in the first place?

Ever the optimist, Davies argues cogently that science should tackle the biggest of questions. He recently moved from Australia to Arizona State University in the United States to set up a sort of cosmic think tank studying "life, the universe and everything", to coin a phrase from Douglas Adams' Hitchhiker's Guide to the Galaxy.

Such herculean efforts are not as far-fetched as they sound. For example, scientists have been searching for some time for a so-called grand unified theory, which would meld together three of nature's fundamental forces. No such all-encompassing theory is currently within reach, but one might be achieved in coming decades.

Would such an ambitious theory explain why the universe exists? Perhaps not directly, Davies suggests. That task might fall to other models, such as the self-explanatory universe that essentially explains itself or, even more amazingly, creates itself. (Now there's a thought, but one upon which I won't elaborate here; you'll need to read the book to find out how!)Another possibility (although this, too, doesn't necessarily explain existence) is that, in the unimaginably distant future, "life and mind will spread out into the cosmos, perhaps from Earth alone, perhaps from many planets. A progressively larger fraction of the universe will be brought under intelligent control".

Under this staggering scenario, a sort of super-duper mind eventually merges with the universe to form what might be regarded as a cosmic mind - or mindful cosmos, if you like.

A heady mix of riveting fundamental science (which Davies is second to none at explaining), theoretical models and some truly wild and weird conjecture, the book is at times so mind-boggling that you are left reeling.

Are we bashing our heads against the limits of human comprehension? Quite possibly: Martin Rees, Britain's Astronomer Royal and arguably one of the brightest people on earth, remarked recently that brains like his were unlikely to be capable of grasping the ultimate nature of reality. So is there hope for the rest of us? Possibly not, if you take a conventional Western perspective.

But other world views offer alternative ways of thinking about fundamental truth, such as some schools of Buddhist thought, which the book does not discuss. Last year, a US-based scholar of Buddhism, James Hughes, sent me an email explaining: "Buddhist ontology argues that all things are empty of enduring nature, and constantly changing, and that the human mind also creates meaning and order out of the universe, where there is no essential meaning and order." This implies that searching for an ultimate reality is futile.

Mathematics, on the other hand, certainly seems to enable physicists to find meaning and order - in a consistent and predictable fashion - throughout the physical world. Might that be because mathematics is a product of the human mind? Platonists, who believe that physical objects are impermanent representations of unchanging ethereal ideals, would say no - but they may not be right.

Davies' book weighs up the welter of pros and cons in the most entertaining and engaging of ways, but stops short, enigmatically, of saying which ideas are right or wrong: for the present, no one really knows.

This gripping tome guarantees two things: it will get you thinking about the deepest matters the human mind can contemplate. And porridge will never seem the same again.

BOOK REVIEW: The Goldilocks Enigma by Paul Davies, Allen Lane, $55

What is it about our universe that allowed life to appear on Earth?That's the crucial question at the heart of Paul Davies' latest book, writes Peter Spinks.

ASKING THE ULTIMATE QUESTIONPeter Spinks