BELIEFS craving for explanation, which is a craving for identity behind diversity, is actually satisfied by the real world; for the real world reveals itself as being in effect a unity in diversity. The craving for explanation was felt by men thousands of years before the instruments, by means of which that craving could be scientifically satisfied, had been invented. The old philosophers of nature assuaged that craving by postulating the existence of some single sub- stance, material or mental, underlying the apparent diversity of independent existents, or by proclaiming that all matter must be built of identically similar atoms, variously arranged. Within the last half-century investigation by means of instruments of precision has actually demonstrated that these cosmological theories which, up till then, could only be described as pieces of wishful thinking designed to satisfy the inborn craving for explanation, were in fact remarkably consonant with die facts of the empirical world. The craving for righteousness seems to be a human character- istic just as fundamental as the craving for explanation. The moral argument in favour of theism is certainly a piece of wishful thinking; but it is no more wishful than the arguments in favour of the atomic theory propounded by Democritus and Epicurus, or even by Boyle and Newton. The theory by means of which these natural philosophers tried to satisfy their craving for explanation was found to be in tolerably close accord with the facts discovered by the later investigators, equipped with more effective instru- ments for exploring physical reality. Whether it will ever be possible to verify the theories of the moral philosphers by direct observation and experiment seems doubtful. But that is no reason for denying the truth of such theories. Nor, as we have seen, is the fact that they originate in wishes. * Tu ne me chercherais pas si tu ne me possidaisj wrote Pascal. 'Ne fingu&te done pas.9 The theories devised to satisfy the craving for explanation have proved 281