People sometimes try to score debating points by saying, Evolution is only a theory. That is correct, but it's important to understand what that means. It is also only a theory that the world goes round the Sun - it's just a theory for which there is an immense amount of evidence. There are many scientific theories that are in doubt. Even within evolution, there is some room for controversy. But that we are cousins of apes and jackals and starfish, let's say, that is a fact in the ordinary sense of the word.

But what, after all, is faith? It is a state of mind that leads people to believe something - it doesn't matter what - in the total absence of supporting evidence. If there were good supporting evidence then faith would be superfluous, for the evidence would compel us to believe it anyway. It is this that makes the often-parroted claim that 'evolution itself is a matter of faith' so silly. People believe in evolution not because they arbitrarily want to believe it but because of overwhelming, publicly available evidence.

Words are our servants, not our masters. For different purposes, we find it convenient to use words in different senses.

Why did God make tigers so good at catching prey, and at the same time make prey so good at getting away from tigers? You'd think that if God wanted one thing or the other to happen he'd have engineered it rather better. Maybe he enjoyed the spectator sport?

Time and again, my sociobiological colleagues have upbraided me as a turncoat, because I will not agree with them that the ultimate criterion for the success of a meme must be its contribution to Darwinian "fitness". At bottom, they insist, a "good meme" spreads because brains are receptive to it, and the receptiveness of brains is ultimately shaped by (genetic) natural selection.

The machine code of the genes is uncannily computer-like. Apart from differences in jargon, the pages of a molecular biology journal might be interchanged with those of a computer engineering journal.

Matthew and Luke handle the problem differently, by deciding that Jesus must have been born in Bethlehem after all. But they get him there by different routes.