This rather made the point, I thought. Levi wrote If this is a Man, not If this is a Chemist. He was a great writer and a chemist, but the two trades were distinct in his mind. Some of his books use chemistry as a frame on which to peg memories of his time in concentration camps. Yet they are not about chemistry in any obvious sense, but about the fundamentals of human life. They use ideas and terms from chemistry to illuminate the world from the side, as it were. The science books that sell, on the other hand, purport to show us the world as it actually is. They have authority.
Chemistry is not the only science excluded from this magic circle. According to Ravi Merchandi, one of the leading scientific publishers in Britain, there are only about four subjects that sell really well: cosmology, evolutionary biology, paleoanthropology, and brain science. But any of these subjects can hit the jackpot - at least in this country. Britain leads the world in the consumption of popular science books. Advances paid for them here are greater, for the size of the population, than anywhere else in the world, and a trend towards larger advances and greater sales for the lucky few has been continuing for the past 20 years.
Other countries are enthusiastic, too, but only for their own authors. The French will buy anything written by a French scientist, the Americans prefer Stephen Jay Gould to Richard Dawkins and so on. This is unlikely to reflect preferences for different perspectives on evolutionary biology. It suggests something deeper and more irrational is at work in the popularity of science.
Why do people buy these books? Merchandi's answer is simple: They provide "grown-up answers to the questions children ask: 'Why are we here? Where are we going? What was in the beginning?' "
This looks like unmitigated good news. To the optimist, sales of popular science books represents the triumph of enlightenment, driving out ignorance and superstition. Religious questions are finally getting scientific answers. The trouble with this optimism is that the evidence suggests that if you ask a religious question, you get a religious answer, whether or not this is dressed up with scientific illustrations.
It would be wonderful if people bought Stephen Hawking and not astrology, but the evidence suggests the same audience buys both. The boom in popular science writing has coincided with a boom in the sort of books that seem diametrically opposed to it. There is nothing so far-fetched and scientifically impossible that you cannot make a decent living publishing books asserting its truth. Against The Double Helix or Wonderful Life are ranged shelves of astrology, homoeopathy for cats, the tomb of Jesus found in the Dordogne, or aromatherapy for dolphins. (I made up only one of these titles.)
More worrying for some scientists was the confusion between legitimate science and pseudo-science in books that purported to be straight. This probably started small, in quantum physics. "There are terrible books written, whose basic premise is that quantum physics is very peculiar, and after quantum physics, anything goes," said John Polkinghorne, a former physicist turned priest.
"There is a tremendous obligation in those who write about science not to stoke up the x factor, but to try lay their matter out in as clear and accessible a way as possible; and to discriminate between mainstream science and the fringe."
John Polkinghorne's own books, it is fair to say, tend to sell to a largely Christian audience and are published by the sober and sensible SPCK. They are not how he makes his living. Anyone trying to sell a book into the wider marketplace has to hype up its importance. This applies still more to the reporting of science, as Tom Wilkie, the former science editor of this newspaper, told the conference.
There was a steady trend, he said, for all types of reporting to move towards the rules of political reporting where both sides are given their say. In this way, he said, the one thing you do not ask yourself is whether the speech you report is true or not, only whether it you are reporting it accurately. It is impossible in political controversies for both sides to be telling the truth. It is possible that both are lying. Yet both are reported as if their views were of equal weight. In general we regard this process as the foundation of democratic debate. Only by trying to give the powerless the same amount of time as the powerful can we ensure debate is fair. But adversarial debate has its own distortions, no less than authoritarianism. When this pattern of reporting is applied to science, the pressure is always to give the cranks equal time with mainstream scientists.
At moments when real science finds itself unable to speak with unequivocal authority, such as the BSE crisis, bad science, pseudo-science and wishful thinking rush to fill the gap.
Ravi Merchandi had seen a link between the consumption of popular science books in Britain and the decline of religion. Here there is another link. For it is a peculiar feature of religious reporting in the secular media that no one ever asks the question of whether it could possibly be true. All religious or metaphysical assertions are treated as equally probable or improbable. Morris Cerullo gets as much space as the Ayatollah Khomeini. The Pope's opinions are treated on a par with George Austin. All that matters is that they make a pretty contrast and entertain the readers.
Science reporting has not reached that stage, at least in the serious media. But there is every sign that it is getting there. The distinction between science and pseudo-science, and even between science and religion, so clear and dear to the scientist, has vanished in the marketplace. It is easy to blame all this on the market. But I think it's wrong to do so. The modern entertainment industry, into which all other human activities are slowly being sucked, is the greatest instrument ever devised for finding out what people want and giving it them. We who serve it may be wrong to do so, but we do not create the desires we satisfy. If the science that consumers want is deeply unscientific, that is not our fault. It is a thought I find profoundly depressing, but perhaps what is wrong with popular science writing is not that it gets the science wrong - for most of it is scrupulously accurate - but that it makes the religion and philosophy involved seem too easy. The thirst for truth, said AE Housman, is the feeblest of all human passions. The lesson I took away from Cambridge is that the longing for certainty is much stronger.