It is not only in our dark hours that scepticism, relativism, hypocrisy, and nihilism dog ethics. Whether it is a matter of giving to charity, or sticking to duty, or insisting on our rights, we can be confused, or be paralysed by the fear that our principles are groundless. Many are afraid that in a Godless world science has unmasked us as creatures fated by our genes to be selfish and tribalisti...