Since time immemorial men have believed in an inner spiritual core of the human personality. All primitive religions hold that man is inhabited by a spirit, however defined. The higher religions claim that man has a soul, that the spiritual nature is the true self, of which the body is a vessel. Since the seventeenth century these notions have been subjected to ever-increasing attacks. The critics of conventional morality include materialists of many different persuasions. However much they differ among themselves, they hold certain principles in common.