It is not easy to say when strictly philosophical thought about religion began, for religion has always involved thought or belief of some kind. Even in other fields much of our thought is incipiently philosophical, but this is much more so in an interest that tends to be all-embracing. Religion has always had a cognitive factor, observances of various kinds had a meaning and these would often be of a far-reaching kind, involving beliefs about an afterlife or the influence upon us of beings other than those who inhabit this world. At what stage such beliefs come to be questioned, and not just accepted as a matter of course or tradition, is difficult to determine. But there is evidence of early questioning of this kind, and of the consequent defense and speculation, in some cultures, for example in India. It...