the ancient and primitive peoples that there is something impure and sinful in the things of sex, so that those who would lead a religious life must avoid sexual relationships; even in India celibacy has commanded respect (see, e.g., Westermarck, _Marriage_, pp. 150 et seq.). As to the original foundation of this notion--which it is unnecessary to discuss more fully here--many theories have been put forward; St. Augustine, in his _De Civitate Dei_, sets forth the ingenious idea that the penis, being liable to spontaneous movements and erections that are not under the control of the will, is a shameful organ and involves the whole sphere of sex in its shame. Westermarck argues that among nearly all peoples there is a feeling against sexual relationship with members of the same family or household, and as sex was thus banished from the sphere of domestic life a notion of its general impurity arose; Northcote points out that from the first it has been necessary to seek concealment for sexual intercourse, because at that moment the couple would be a prey to hostile attacks, and that it was by an easy transition that sex came to be regarded as a thing that ought to be concealed, and, therefore, a sinful thing. (Diderot, in his _Supplément au Voyage de Bougainville_, had already referred to this motive for seclusion as "the only natural element in modesty.") Crawley has devoted a large part of his suggestive work, _The Mystic Rose_, to showing that, to savage man, sex is a perilous, dangerous, and enfeebling element in life, and, therefore, sinful.