Westermarck[181] advanced the following to explain the dread of incest: “that an innate aversion against sexual intercourse exists between persons who live together from childhood and that this feeling, since such persons are as a rule consanguineous, finds a natural expression in custom and law through the abhorrence of sexual intercourse between those closely related.” Though Havelock Ellis disputed the instinctive character of this aversion in the _Studies in the Psychology of Sex_, he otherwise supported the same explanation in its essentials by declaring: “The normal absence of the manifestation of the pairing instinct where brothers and sisters or boys and girls living together from childhood are concerned, is a purely negative phenomenon due to the fact that under these circumstances the antecedent conditions for arousing the mating instinct must be entirely lacking.... For persons who have grown up together from childhood habit has dulled the sensual attraction of seeing, hearing and touching and has led it into a channel of quiet attachment, robbing it of its power to call forth the necessary erethistic excitement required to produce sexual tumescence.” It seems to me very remarkable that Westermarck looks upon this innate aversion to sexual intercourse with persons with whom we have shared childhood as being at the same time a psychic representative of the biological fact that inbreeding means injury to the species. Such a biological instinct would hardly go so far astray in its psychological manifestation as to affect the companions of home and hearth which in this respect are quite harmless, instead of the blood relatives which alone are injurious to procreation. And I cannot resist citing the excellent criticism which Frazer opposes to Westermarck’s assertion. Frazer finds it incomprehensible that sexual sensibility to-day is not at all opposed to sexual intercourse with companions of the hearth and home while the dread of incest, which is said to be nothing but an offshoot of this reluctance, has nowadays grown to be so overpowering. But other remarks of Frazer’s go deeper and I set them down here in unabbreviated form because they are in essential agreement with the arguments developed in my chapter on taboo.