3 Preface وَالشَّفعِ وَالوَترِYusuf AliBy the Even and Odd (contrasted);1The contrast between even and odd forms the subject of learned argument among those who deal with the mystic properties of numbers. In any case, even and odd follow each other in regular succession: each is independent, and yet neither is self-sufficient. In ultimate analysis every even number is a pair of odd ones. And all things go in pairs: see 36:36, and the n. to 36:36. In the animal world pairs are but two individuals, and yet each is a complement of the other. Both abstract and concrete things are often understood in contrast with their opposites. Why should we not, in spiritual matters, understand this life better with reference to the Hereafter, and why should we disbelieve in the Hereafter simply because we cannot conceive of anything different from our present life?