Westermarck next takes up the origin of prohibited degrees; and after a critical examination of the various theories to explain it, he comes to the conclusion that in no case observed is the prohibition of incest founded on conscious experience of its injurious effects. It has not come into existence as the result of observation or calculation or through education on the part of the savage. Law and custom might thus arise; and these may "prevent passion from passing into action, they cannot wholly destroy its inward power." The home is kept pure "neither by laws, nor by customs, nor by education, but by an _instinct_ which under normal circumstances makes sexual love between the nearest kin a psychical impossibility." But this instinct is not an "_innate_ aversion to marriage with _near relations_." It is rather an "innate aversion to sexual intercourse between persons living very closely together from early youth;" and "as such persons are in most cases related, this feeling displays itself chiefly as a horror of intercourse between near kin." It is not "by the degrees of consanguinity, but by the close living together that prohibitory laws against intermarriage are determined."[384] [384] _Ibid._, 318, 320, 321. WAKE, _Marriage and Kinship_, 55, 56, expresses a similar view. This theory, it will be noticed, coincides with that of Starcke in selecting local contiguity or the intimate association of family life as the fundamental fact. It differs, however, in several important particulars. The economic or legal motives are not emphasized; and Westermarck's explanation is broader than Starcke's, for he holds that the aversion extends to sexual connections outside of regular marriage.