A further reason some people avoid giving numbers is that they don’t want to be pinned down, preferring the cloak of vagueness that comes with natural language. But I’d love to be pinned down, to lay my cards on the table and let others see if improvements can be made. It is only through such clarity and openness to being refuted that we make intellectual progress.

Mr. Buffon, from our disregard of the possibility of death within the four-and-twenty hours, concludes that a chance which falls below or rises above ten thousand to one will never affect the hopes or fears of a reasonable man. The fact is true, but our courage is the effect of thoughtlessness, rather than of reflection. If a public lottery were drawn for the choice of an immediate victim, and if our name were inscribed on one of the ten thousand tickets, should we be perfectly easy?

Once we acknowledge the risk/uncertainty distinction, it is natural to think that our default state is uncertainty. Getting to a position where we can legitimately treat a proposition as risky is a cognitive achievement. Traditional indifference principles fail because they trivialise this achievement.

Probability is the guide of life, and of death, too.