(M151) Perhaps customs of this sort have left traces of themselves in Greek myth and legend. Cronus or Saturn, as the Romans called him, is said to have been the youngest son of the sky-god Uranus, and to have mutilated his father and reigned in his stead as king of gods and men. Afterwards he was warned by an oracle that he himself should be deposed by his son. To prevent that catastrophe Cronus swallowed his children, one after the other, as soon as they were born. Only the youngest of them, Zeus, was saved through a trick of his mother’s, and in time he fulfilled the oracle by banishing his father and sitting on his throne. But Zeus in his turn was told that his wife Metis would give birth to a son who would supplant him in the kingdom of heaven. Accordingly, to rid himself of his future rival he resorted to a device like that which his father Cronus had employed for a similar purpose. Only instead of waiting till the child was born and then devouring it, he made assurance doubly sure by swallowing his wife with the unborn babe in her womb.(519) Such barbarous myths become intelligible if we suppose that they took their rise among people who were accustomed to see grown-up sons supplanting their fathers by force, and fathers murdering and perhaps eating their infants in order to secure themselves against their future rivalry. We have met with instances of savage tribes who are said to devour their firstborn children.(520) (M152) The legend that Laius, king of Thebes, exposed his infant son Oedipus, who afterwards slew his father and sat on the throne, may well be a reminiscence of a state of things in which father and son regularly plotted against each other. The other feature of the story, to wit the marriage of Oedipus with the widowed queen, his mother, fits in very well with the rule which has prevailed in some countries that a valid title to the throne is conferred by marriage with the late king’s widow. That custom probably arose, as I have endeavoured to shew,(521) in an age when the blood-royal ran in the female line, and when the king was a man of another family, often a stranger and foreigner, who reigned only in virtue of being the consort of a native princess, and whose sons never succeeded him on the throne. But in process of time, when fathers had ceased to regard the birth of a son as a menace to their life, or at least to their regal power, kings would naturally scheme to secure the succession for their own male offspring, and this new practice could be reconciled with the old one by marrying the king’s son either to his own sister or, after his father’s decease, to his stepmother. We have seen marriage with a stepmother actually enjoined for this very purpose by some of the Saxon kings.(522) And on this hypothesis we can understand why the custom of marriage with a full or a half sister has prevailed in so many royal families.(523) It was introduced, we may suppose, for the purpose of