That is not all. The problem of death early engaged the attention of primitive people. They considered it altogether as a physical affair; they explained it, as Messrs. Tylor and Spencer (following Lucretius) have shown, by a number of inductions drawn from observations on sleep, lethargy, and dream. A sleeping body awakes, it seems to follow that a dead body will awake; that is the line of reasoning. Moreover, the dead come back in dreams, or in the demi-hallucinations of the night and of fear. The modern conception of pure spirit is an indirect and later consequence of a belief in immortality, it is not itself the principle of it. A cult for the dead, for the manes, as the Romans said, is partly explicable on moral or psychological grounds, as, for example, by a prolongation of filial respect and fear, and partly on grounds altogether material and gross. A cult for the dead rests on a naïve theory based on sentiment; it is semi-physical and semi-psychological. The nature of a departed soul has been conceived in very different ways. Among the Dakota Indians of North America, one’s double goes up into the air, one’s _third_ rejoins the spirits, one’s fourth and last soul stays by the body; an instance of a very complicated theory formed out of elements altogether primitive. In general, the belief is that the souls of the dead go to join ancestral souls in another world, which is commonly a distant land from which the tribe has migrated in former times—affording an example of a social tie which survives death. The Greeks and Romans believed that, if the body was deprived of sepulture, its shadow could not penetrate into its proper place of abode; it remained on earth and haunted the living—a remnant of former beliefs in the necessity of sepulture and the maintenance of friendly relations with the society of the dead.[36] [36] See the author’s _Morale d’Épicure_ (_Des idées antiques sur la mort_) 3d edition, p. 105. [Sidenote: Analogies between ghosts and living people.] The dead were to be conciliated by the same means as the living, by supplications and gifts. The gifts were the same as those which are acceptable to the living—food, arms, costumes, horses, servants. In Dahomey, when a king dies, a hundred of his soldiers are immolated on his tomb as a body guard. Much the same thing was done among the Incas of Peru. At Bali all the women of the harem are immolated upon the grave of the defunct sultan. In Homer, Achilles slaughtered his Trojan prisoners on the funeral pyre of Patroclus, together with the horses and the dogs of his dead friend. The Fiji islanders used to immolate a man at the foot of each pillar in the home of a chief, as a guard for the edifice. In our days, spirits are still so numerous, in the eyes of certain people, that an Arab, for example, when he throws a stone, breathes an apology to such spirits as he may strike.[37] The universe is populated by anthropomorphic societies.