Murder, which is the summit of evil-doing according to human canons is at the same time the most natural act in the world. The so-called “unwritten law” which weighs up the evidence in favour of a man who kills his wife’s lover, is not without justice and a sense of fair play. In England, there is plenty of unwritten law, but it has nothing whatever to do with the _crime passionel_. However, if _A_ enters the bedroom of his wife and discovers this unfortunate woman with _B_, _in flagrante delicto_, to misuse an expression, and he shoots _B_ on the spot, he stands a very good chance of escaping the supreme punishment of the law. But if _A_, on seeing his wife in the act of adultery with _B_, leaves the room, goes downstairs, obtains possession of his revolver, and then returns to kill _B_, the position is somewhat different. This particular example supplies evidence of _mens rea_, or criminal intent. _A_ is not acting in a spontaneous fashion, for he deliberately goes away and then returns, with murder in his mind. In a good many parts of the world, either way would be justifiable, and, one must admit, with some reason. There is nothing more far-reaching than adultery in a married woman. Her future offspring may not be that of her husband, and, at best, he believes her body to be tainted with a poisonous contact. The real idea of marriage is to keep one woman exclusively for one man, by whom it is intended she should fulfil the functions of maternity. To have suspicion of outside intercourse is to destroy everything which is most profound in the union. It is usual to divorce a wife who commits adultery, in England: to kill her lover and to ostracise her from her home are methods left to other races.