The Golden Bough

by James George Frazer

Similar cases of incest with a daughter are reported of many ancient kings. It seems unlikely that such reports are without foundation, and perhaps equally improbable that they refer to mere fortuitous outbursts of unnatural lust. We may suspect that they are based on a practice actually observed for a definite reason in certain special circumstances. Now in countries where the royal blood was traced through women only, and where consequently the king held office merely in virtue of his marriage with an hereditary princess, who was the real sovereign, it appears to have often happened that a prince married his own sister, the princess royal, in order to obtain with her hand the crown which otherwise would have gone to another man, perhaps to a stranger. May not the same rule of descent have furnished a motive for incest with a daughter? For it seems a natural corollary from such a rule that the king was bound to vacate the throne on the death of his wife, the queen, since he occupied it only by virtue of his marriage with her. When that marriage terminated, his right to the throne terminated with it and passed at once to his daughter’s husband. Hence if the king desired to reign after his wife’s death, the only way in which he could legitimately continue to do so was by marrying his daughter, and thus prolonging through her the title which had formerly been his through her mother.