Altruism and tolerance make sense only by being paradoxical. It is impossible to be tolerant of someone else’s behaviour – a neighbour playing loud music, for example – unless you disapprove of it in the first place. If you approve of something, you like or admire it, tolerance is unnecessary. Altruism is similar. It is impossible for someone to be altruistic, to give unselfishly, unless someone else is selfish enough to take. A purely altruistic society is impossible: we would all end up passing presents to each other like saints in a never-ending circle.