In 434 Prince Karu, then Heir to the Throne, fell in love with his younger sister by the same mother. At first he dreaded the guilt and was silent. But after a time he yielded to his passion. The next year, in the height of summer, the soup for the Mikado's meal froze and became ice. The diviner said, "There is domestic disorder (incest)." This led to the discovery of Prince Karu's crime, but, as he was successor to the Throne, he was not punished, and his sister only was sent into banishment. After his father's death, however, the ministers and people refused him their allegiance, and he ultimately committed suicide, or, according to another version of the story, went into exile. It is difficult to say whether the religious or the merely moral element predominates in such a case. The portent by which the Prince's crime was followed and the application to the diviners indicate that the crime was thought offensive to the Gods. On the other hand, banishment is a civil form of punishment, and the idea that the offence might bring disaster on the community was probably at the root of the indignation which it caused. Nor is it to be forgotten that there is another non-religious reason for the law against incest. Consanguineous unions are notoriously unfavourable to the propagation of a numerous and healthy progeny, and therefore to the welfare of the community. The 'Chüen,' a Chinese work written several centuries before the Christian era, says: "When the man and woman are of the same surname, the race does not continue." But in China too, the religious sanction of the prohibition of incest is not absent. It is one of those primarily non-religious sexual taboos, having for their object to place a check on masculine tyranny over the weaker sex and the premature, promiscuous, and excessive indulgence of the sexual passion which even savages find to be fatal to the welfare of the individual and the community, and whose transcendent importance and the difficulty of enforcing them by law lead to be reinforced everywhere by religious terrors. The prohibition of unions between brothers and sisters by the mother's side--that is, practically of the full blood--and not of those of the half-blood by the father's side, may be partly due to the circumstance that the former are more commonly brought up together, and a check on immature and consanguineous intercourse was more necessary in their case. This taboo very likely dates from a period when parentage was reckoned chiefly by maternity. Vulgar licentiousness is not mentioned in the more ancient books as causing ceremonial impurity. Interference with the virgin priestesses was not only a source of uncleanness, but was in some cases severely punished. The _Nihongi_ states that in A.D. 465