We would not waste time saying so because nobody, so far as I know, worships teapots;*) but, if pressed, we would not hesitate to declare our strong belief that there is positively no orbiting teapot. Yet strictly we should all be teapot agnostics: we cannot prove, for sure, that there is no celestial teapot. In practice, we move away from teapot agnosticism towards a-teapotisin.

A friend, who was brought up a Jew and still observes the sabbath and other Jewish customs out of loyalty to his heritage, describes himself as a 'tooth fairy agnostic'. He regards God as no more probable than the tooth fairy. You can't disprove either hypothesis, and both are equally improbable. He is an a-theist to exactly the same large extent that he is an a-fairyist. And agnostic about both, to the same small extent.

Russell's teapot, of course, stands for an infinite number of things whose existence is conceivable and cannot be disproved. That great American lawyer Clarence Darrow said, 'I don't believe in God as I don't believe in Mother Goose.' The journalist Andrew Mueller is of the opinion that pledging yourself to any particular religion 'is no more or less weird than choosing to believe that the world is rhombus-shaped, and borne through the cosmos in the pincers of two enormous green lobsters called Esmerelda and Keith'.³² A philosophical favourite is the invisible, intangible, inaudible unicorn, disproof of which is attempted yearly by the children at Camp Quest.*) A popular deity on the Internet at present — and as undisprovable as Yahweh or any other — is the Flying Spaghetti Monster, who, many claim, has touched them with his noodly appendage.³³ I am delighted to see that the Gospel of the Flying Spaghetti Monster has now been published as a book,³⁴ to great acclaim. I haven't read it myself, but who needs to read a gospel when you just know it's true? By the way, it had to happen — a Great Schism has already occurred, resulting in the Reformed Church of the Flying Spaghetti Monster.³⁵

The point of all these way-out examples is that they are undisprovable, yet nobody thinks the hypothesis of their existence is on an even footing with the hypothesis of their non-existence. Russell's point is that the burden of proof rests with the believers, not the non-believers. Mine is the related point that the odds in favour of the teapot (spaghetti monster / Esmerelda and Keith / unicorn etc.) are not equal to the odds against.

The fact that orbiting teapots and tooth fairies are undisprovable is not felt, by any reasonable person, to be the kind of fact that settles any interesting argument. None of us feels an obligation to disprove any of the millions of far-fetched things that a fertile or facetious imagination might dream up. I have found it an amusing strategy, when asked whether I am an atheist, to point out that the questioner is also an atheist when considering Zeus, Apollo, Amon Ra, Mithras, Baal, Thor, Wotan, the Golden Calf and the Flying Spaghetti Monster. I just go one god further.

All of us feel entitled to express extreme scepticism to the point of outright disbelief — except that in the case of unicorns, tooth fairies and the gods of Greece, Rome, Egypt and the Vikings, there is (nowadays) no need to bother. In the case of the Abrahamic God, however, there is a need to bother, because a substantial proportion of the people with whom we share the planet do believe strongly in his existence. Russell's teapot demonstrates that the ubiquity of belief in God, as compared with belief in celestial teapots, does not shift the burden of proof in logic, although it may seem to shift it as a matter of practical politics. That you cannot prove God's non-existence is accepted and trivial, if only in the sense that we can never absolutely prove the non-existence of anything. What matters is not whether God is disprovable (he isn't) but whether his existence is probable. That is another matter. Some undisprovable things are sensibly judged far less probable than other undisprovable things. There is no reason to regard God as immune from consideration along the spectrum of probabilities. And there is certainly no reason to suppose that, just because God can be neither proved nor disproved, his probability of existence is 50 per cent. On the contrary, as we shall see.

Just as Thomas Huxley bent over backwards to pay lip service to completely impartial agnosticism, right in the middle of my seven-stage spectrum, theists do the same thing from the other direction, and for an equivalent reason. The theologian Alister McGrath makes it the central point of his book Dawkins' God: Genes, Memes and the Origin of Life. Indeed, after his admirably fair summary of my scientific works, it seems to be the only point in rebuttal that he has to offer: the undeniable but ignominiously weak point that you cannot disprove the existence of God. On page after page as I read McGrath, I found myself scribbling 'teapot' in the margin. Again invoking T. H. Huxley, McGrath says, 'Fed up with both theists and atheists making hopelessly dogmatic statements on the basis of inadequate empirical evidence, Huxley declared that the God question could not be settled on the basis of the scientific method.'

McGrath goes on to quote Stephen Jay Gould in similar vein: 'To say it for all my colleagues and for the umpteenth millionth time (from college bull sessions to learned treatises): science simply cannot (by its legitimate methods) adjudicate the issue of God's possible superintendence of nature. We neither affirm nor deny it; we simply can't comment on it as scientists.' Despite the confident, almost bullying, tone of Gould's assertion, what, actually, is the justification for it? Why shouldn't we comment on God, as scientists? And why isn't Russell's teapot, or the Flying Spaghetti Monster, equally immune from scientific scepticism? As I shall argue in a moment, a universe with a creative superintendent would be a very different kind of universe from one without. Why is that not a scientific matter?

Gould carried the art of bending over backwards to positively supine lengths in one of his less admired books, Rocks of Ages. There he coined the acronym NOMA for the phrase 'non-overlapping magisterial:

This sounds terrific — right up until you give it a moment's thought. What are these ultimate questions in whose presence religion is an honoured guest and science must respectfully slink away?

Martin Rees, the distinguished Cambridge astronomer whom I have already mentioned, begins his book Our Cosmic Habitat by posing two candidate ultimate questions and giving a NOMA-friendly answer. 'The pre-eminent mystery is why anything exists at all. What breathes life into the equations, and actualized them in a real cosmos? Such questions lie beyond science, however: they are the province of philosophers and theologians.' I would prefer to say that if indeed they lie beyond science, they most certainly lie beyond the province of theologians as well (I doubt that philosophers would thank Martin Rees for lumping theologians in with them). I am tempted to go further and wonder in what possible sense theologians can be said to have a province. I am still amused when I recall the remark of a former Warden (head) of my Oxford college. A young theologian had applied for a junior research fellowship, and his doctoral thesis on Christian theology provoked the Warden to say, 'I have grave doubts as to whether it's a subject at all.'