Gravity is not a version of the truth. It is the truth. Anybody who doubts it is invited to jump out of a tenth-floor window. - Richard Dawkins

It is often said, mainly by the 'no-contests', that although there is no positive evidence for the existence of God, nor is there evidence against his existence. So it is best to keep an open mind and be agnostic. At first sight that seems an unassailable position, at least in the weak sense of Pascal's wager. But on second thoughts it seems a cop-out, because the same could be said of Father Christmas and tooth fairies. There may be fairies at the bottom of the garden. There is no evidence for it, but you can't prove that there aren't any, so shouldn't we be agnostic with respect to fairies?

Orb webs in real life do their business largely in two dimensions. If the mesh is too coarse, flies pass straight through. If the mesh is too fine, rival spiders will achieve nearly the same result at less cost in silk, and will therefore leave behind more progeny to carry on their economically more prudent genes. Natural selection finds the efficient compromise.

The patient typically finds himself impelled by some deep, inner conviction that something is true, or right, or virtuous: a conviction that doesn't seem to owe anything to evidence or reason, but which, nevertheless, he feels as totally compelling and convincing. We doctors refer to such a belief as "faith".