Historical Summary

But if the incest tabu and incest groups originated in an exchange of courtesies which developed into a calculated policy, without innate aversion to sex unions with near kindred, what would be the explanation of the horror which incestuous unions excite? The explanation would be that the violation of any habit system arouses emotional resistance, and there are numerous cases where the violation of habits which have no basis in organic repugnance evokes horror equivalent to the horror of incest. We have seen, for example, that marriage with a wife’s sister and with a deceased wife’s sister were among the usual and in some cases obligatory marriages among primitive groups, but in modern England the situation became so defined that marriage with a deceased wife’s sister became equivalent to incest and the thought of such marriage was defined as "psychic incest." It was argued that it would be impossible to have pure thoughts about a wife’s younger sister in the household if marriage with her were ever possible. Around the year 1850, when Lord Russell’s bill for the repeal of the law against such marriages was being debated, countless sermons were preached and thousands of pamphlets and letters were printed protesting against repeal: