I do have one thing in common with the creationists. Like me, but unlike the 'Chamberlain school', they will have no truck with NOMA and its separate magisteria. Far from respecting the separateness of science's turf, creationists like nothing better than to trample their dirty hobnails all over it. And they fight dirty, too. Lawyers for creationists, in court cases around the American boondocks, seek out evolutionists who are openly atheists. I know — to my chagrin — that my name has been used in this way. It is an effective tactic because juries selected at random are likely to include individuals brought up to believe that atheists are demons incarnate, on a par with pedophiles or 'terrorists' (today's equivalent of Salem's witches and McCarthy's Commies). Any creationist lawyer who got me on the stand could instantly win over the jury simply by asking me: 'Has your knowledge of evolution influenced you in the direction of becoming an atheist?' I would have to answer yes and, at one stroke, I would have lost the jury. By contrast, the judicially correct answer from the secularist side would be: 'My religious beliefs, or lack of them, are a private matter, neither the business of this court nor connected in any way with my science.' I couldn't honestly say this, for reasons I shall explain in Chapter 4.

The Guardian journalist Madeleine Bunting wrote an article entitled 'Why the intelligent design lobby thanks God for Richard Dawkins'.⁴¹ There's no indication that she consulted anybody except Michael Ruse, and her article might as well have been ghostwritten by him.*) Dan Dennett replied, aptly quoting Uncle Remus:

This whole issue, including an independent invocation of Brer Rabbit in the briar patch, is well discussed by the biologist P. Z. Myers, whose Pharyngula blog can reliably be consulted for trenchant good sense.⁴³

I am not suggesting that my colleagues of the appeasement lobby are necessarily dishonest. They may sincerely believe in NOMA, although I can't help wondering how thoroughly they've thought it through and how they reconcile the internal conflicts in their minds. There is no need to pursue the matter for the moment, but anyone seeking to understand the published statements of scientists on religious matters would do well not to forget the political context: the surreal culture wars now rending America. NOMA-style appeasement will surface again in a later chapter. Here, I return to agnosticism and the possibility of chipping away at our ignorance and measurably reducing our uncertainty about the existence or non-existence of God.

Suppose Bertrand Russell's parable had concerned not a teapot in outer space but life in outer space — the subject of Sagan's memorable refusal to think with his gut. Once again we cannot disprove it, and the only strictly rational stance is agnosticism. But the hypothesis is no longer frivolous. We don't immediately scent extreme improbability. We can have an interesting argument based on incomplete evidence, and we can write down the kind of evidence that would decrease our uncertainty. We'd be outraged if our government invested in expensive telescopes for the sole purpose of searching for orbiting teapots. But we can appreciate the case for spending money on SETI, the Search for Extraterrestrial Intelligence, using radio telescopes to scan the skies in the hope of picking up signals from intelligent aliens.

I praised Carl Sagan for disavowing gut feelings about alien life. But one can (and Sagan did) make a sober assessment of what we would need to know in order to estimate the probability. This might start from nothing more than a listing of our points of ignorance, as in the famous Drake Equation which, in Paul Davies's phrase, collects probabilities. It states that to estimate the number of independently evolved civilizations in the universe you must multiply seven terms together. The seven include the number of stars, the number of Earth-like planets per star, and the probability of this, that and the other which I need not list because the only point I am making is that they are all unknown, or estimated with enormous margins of error. When so many terms that are either completely or almost completely unknown are multiplied up, the product — the estimated number of alien civilizations — has such colossal error bars that agnosticism seems a very reasonable, if not the only credible stance.

Some of the terms in the Drake Equation are already less unknown than when he first wrote it down in 1961. At that time, our solar system of planets orbiting a central star was the only one known, together with the local analogies provided by Jupiter's and Saturn's satellite systems. Our best estimate of the number of orbiting systems in the universe was based on theoretical models, coupled with the more informal 'principle of mediocrity': the feeling (born of uncomfortable history lessons from Copernicus, Hubble and others) that there should be nothing particularly unusual about the place where we happen to live. Unfortunately, the principle of mediocrity is in its turn emasculated by the 'anthropic' principle (see Chapter 4): if our solar system really were the only one in the universe, this is precisely where we, as beings who think about such matters, would have to be living. The very fact of our existence could retrospectively determine that we live in an extremely unmediocre place.

But today's estimates of the ubiquity of solar systems are no longer based on the principle of mediocrity; they are informed by direct evidence. The spectroscope, nemesis of Comte's positivism, strikes again. Our telescopes are scarcely powerful enough to see planets around other stars directly. But the position of a star is perturbed by the gravitational pull of its planets as they whirl around it, and spectroscopes can pick up the Doppler shifts in the star's spectrum, at least in cases where the perturbing planet is large. Mostly using this method, at the time of writing we now know of 170 extra-solar planets orbiting 147 stars,⁴⁴ but the figure will certainly have increased by the time you read this book. So far, they are bulky 'Jupiters', because only Jupiters are large enough to perturb their stars into the zone of detectability of present-day spectroscopes.