To return to the infinite regress and the futility of invoking God to terminate it, it is more parsimonious to conjure up, say, a 'big bang singularity', or some other physical concept as yet unknown. Calling it God is at best unhelpful and at worst perniciously misleading. Edward Lear's Nonsense Recipe for Crumboblious Cutlets invites us to 'Procure some strips of beef, and having cut them into the smallest possible pieces, proceed to cut them still smaller, eight or perhaps nine times.' Some regresses do reach a natural terminator. Scientists used to wonder what would happen if you could dissect, say, gold into the smallest possible pieces. Why shouldn't you cut one of those pieces in half and produce an even smaller smidgen of gold? The regress in this case is decisively terminated by the atom. The smallest possible piece of gold is a nucleus consisting of exactly seventy-nine protons and a slightly larger number of neutrons, attended by a swarm of seventy-nine electrons. If you 'cut' gold any further than the level of the single atom, whatever else you get it is not gold. The atom provides a natural terminator to the Crumboblious Cutlets type of regress. It is by no means clear that God provides a natural terminator to the regresses of Aquinas. That's putting it mildly, as we shall see later. Let's move on down Aquinas' list.

That's an argument? You might as well say, people vary in smelliness but we can make the comparison only by reference to a perfect maximum of conceivable smelliness. Therefore there must exist a pre-eminently peerless stinker, and we call him God. Or substitute any dimension of comparison you like, and derive an equivalently fatuous conclusion.

The argument from design is the only one still in regular use today, and it still sounds to many like the ultimate knockdown argument. The young Darwin was impressed by it when, as a Cambridge undergraduate, he read it in William Paley's Natural Theology. Unfortunately for Paley, the mature Darwin blew it out of the water. There has probably never been a more devastating rout of popular belief by clever reasoning than Charles Darwin's destruction of the argument from design. It was so unexpected. Thanks to Darwin, it is no longer true to say that nothing that we know looks designed unless it is designed. Evolution by natural selection produces an excellent simulacrum of design, mounting prodigious heights of complexity and elegance. And among these eminences of pseudo-design are nervous systems which — among their more modest accomplishments — manifest goal-seeking behaviour that, even in a tiny insect, resembles a sophisticated heat-seeking missile more than a simple arrow on target. I shall return to the argument from design in Chapter 4.

Arguments for God's existence fall into two main categories, the a priori and the a posteriori. Thomas Aquinas' five are a posteriori arguments, relying upon inspection of the world. The most famous of the a priori arguments, those that rely upon pure armchair ratiocination, is the ontological argument, proposed by St Anselm of Canterbury in 1078 and restated in different forms by numerous philosophers ever since. An odd aspect of Anselm's argument is that it was originally addressed not to humans but to God himself, in the form of a prayer (you'd think that any entity capable of listening to a prayer would need no convincing of his own existence).

It is possible to conceive, Anselm said, of a being than which nothing greater can be conceived. Even an atheist can conceive of such a superlative being, though he would deny its existence in the real world. But, goes the argument, a being that doesn't exist in the real world is, by that very fact, less than perfect. Therefore we have a contradiction and, hey presto, God exists!

Let me translate this infantile argument into the appropriate language, which is the language of the playground:

I had my childish wiseacre choose the word 'fools' advisedly. Anselm himself quoted the first verse of Psalm 14, 'The fool hath said in his heart, There is no God,' and he had the cheek to use the name 'fool' (Latin insipiens) for his hypothetical atheist:

The very idea that grand conclusions could follow from such logo-machist trickery offends me aesthetically, so I must take care to refrain from bandying words like 'fool'. Bertrand Russell (no fool) interestingly said, 'It is easier to feel convinced that [the ontological argument] must be fallacious than it is to find out precisely where the fallacy lies.' Russell himself, as a young man, was briefly convinced by it:

Why, I wonder, didn't he say something like: 'Great Scott, the ontological argument seems to be plausible. But isn't it too good to be true that a grand truth about the cosmos should follow from a mere word game? I'd better set to work to resolve what is perhaps a paradox like those of Zeno.' The Greeks had a hard time seeing through Zeno's 'proof that Achilles would never catch the tortoise.*) But they had the sense not to conclude that therefore Achilles really would fail to catch the tortoise. Instead, they called it a paradox and waited for later generations of mathematicians to explain it (with, as it turned out, the theory of infinite series converging on a limiting value). Russell himself, of course, was as well qualified as anyone to understand why no tobacco tins should be thrown up in celebration of Achilles' failure to catch the tortoise. Why didn't he exercise the same caution over St Anselm? I suspect that he was an exaggeratedly fair-minded atheist, over-eager to be disillusioned if logic seemed to require it.*) Or perhaps the answer lies in something Russell himself wrote in 1946, long after he had rumbled the ontological argument: