Morality, then, is not a set of arbitrary regulations dictated by a vengeful deity and written down in a book; nor is it the custom of a particular culture or tribe. It is a consequence of the interchangeability of perspectives and the opportunity the world provides for positive-sum games.

The Better Angels of Our Nature: The Decline of Violence In History And Its Causes (ed. Penguin UK, 2011) - ISBN: 9780141959740