Weidenfeld, 326pp, £20

John Horgan likes to tease. While a reporter for Scientific American, his barbed style always stood in uneasy contrast with the more naturally fawning tone of the journal. And when he departed to write his first book - one proclaiming that science has no more truly big discoveries to make - it was a minor triumph of controversy.

With some relish, Horgan describes the subsequent outrage of a London biology professor who, bumping into him at a conference, shrieked that the book was "Appalling! Absolutely appalling!" "For a thrilling instant I thought he was going to strike me," confides Horgan.

What riled readers of The End of Science was the semi-reasonableness of Horgan's claims. He was saying that for scientists most of the easy gains have already been made and what now remains is either filling in the fine detail or else tackling questions which are in principle impossible to solve - such as why there should be a Universe at all or what is the secret of human consciousness?

Mostly Horgan managed to stay the right side of provoking without getting plain silly. Yet many - including the irate professor - felt he was on rather shaky ground in suggesting that consciousness lay beyond scientific reach. With The Undiscovered Mind, Horgan returns to the debate to argue that even if there were cause to dream about a grand unified theory of consciousness, it is hard to see how the current mob of researchers could possibly deliver.

Quite rightly, Horgan paints a depressing picture of a field in some disarray. He offers a thumbnail sketch of every discipline that feels it has something to say about the mind, from genetics to psychoanalysis, from artificial intelligence to neuroscience. The tone is light. The book is filled with witty accounts of Horgan's encounters with the famous and not so famous. There is the psychiatrist's annual convention with a foyer filled with lavish displays from drug companies. A 20ft high gold obelisk celebrates Prozac. Horgan sardonically notes that the lone dissenting voice to this crass show of chemo-fetishism comes from the salesman at a modest little booth for Somatics Inc - a company that peddles his- and her-sized reusable mouthguards to minimise tooth fracture during electric shock treatment.

A large part of the book is given over to judging mind scientists by the practical applications of their multifarious theories. Horgan neatly sums up the evidence that pills, shock treatment and psychoanalysis are all about equally effective - or rather, ineffective - in treating mental illness. Computer science may produce champion-beating chess programs but it still remains light-years from creating the most rudimentary forms of intelligence. Even the bright new sciences of brain imaging and gene mapping are deemed failures, as each trumpeted discovery, like the gene for homosexuality or shrunken brains in schizophrenia, tends to evaporate under closer scrutiny. The small returns from each field are contrasted with the often quite grotesque confidence of its practitioners.

Horgan's conclusion is that while all this busy science is producing the occasional crumbs of knowledge, there is no sign of an Einstein-like figure who is eventually going to draw the whole story together, so substantiating his claim that mind researchers will be able to accumulate trivial facts and spin fanciful theories until the end of time without ever really getting their heads around their subject.

So is Horgan right? He is certainly correct about the astonishing lack of cohesion in the mind sciences and also, importantly, about the nature of the breakthrough that people actually demand. He writes : "They yearn for an insight so powerful that it will instantly dispel the mystery from consciousness, like the sun burning off a morning fog. They seek not just an explanation but a revelation."

Yet Horgan fails to note that over the past decade a wrenching paradigm shift has been taking place in neuroscience, if not yet in the more peripheral fields on which he mostly concentrates. Even in neuroscience, it is true that many researchers still display a naive reductionism - they hope for one shining fact about the brain that will illuminate the mystery. However, Horgan does not report on the many others who have now accepted that consciousness is the result of immense complexity and so any sense of understanding will have to come from mastering a mass of detail.

They see their job as getting under the skin of a biological organ and achieving a feel for the very organic way that information pulses and flows through its pathways. Rather than processing information in the familiar step-by-step fashion of a computer, the nervous system seems more to evolve a state of focused representation. It contracts to wrap itself tightly around the shape of each passing moment. While it is still early days for this dynamic view, Horgan does not even consider its potential for pulling together a vast amount of already known facts to create a satisfying whole.

That aside, being in Horgan's company is to travel with a curious and cynical soul as he bumps entertainingly about the current landscape of mind science. The picture is painted in bright dabs of colour and there is little of the daunting neurology that has left so many of the recent crop of consciousness books unread. Contrary to his arguments, brain research probably does have a future to which to look forward. But meanwhile, Horgan has put his case much too charmingly, indeed too mildly, for him to need to fear a punch on the nose the next time he shows his face at a conference.