In 1891 the Finnish sociologist Edward Westermarck published The history of human marriage, considered a founding text for modern studies of the family in that it broke sharply with a number of evolutionist presuppositions. Westermarck claimed that the incest prohibition derived from an innate aversion to sexual relations between persons who had lived together since early youth. Westermarck’s claim was soon contested, namely by Émile Durkheim and Sigmund Freud, and an important discussion developed that constitutes a matrix of the sociology/psychoanalysis debate. I retrace the development and configuration of this controversy, then identify some of the main issues : the unconscious meaning of the incest fear, the cultural dimension of the incest prohibition, the social status associated with this particular transgression. This in turn leads to identifying differences in how the theme of incest is handled not only in the social sciences versus psychoanalysis but also in the distinct social sciences of sociology and anthropology. I bring to light the necessarily transferential aspect of this problematic.