Against the background of degeneration and the perceived threat to the nation’s health and stock, family politics came to constitute an important site for eugenic discourses and interventions. Eugenic regulation of reproductive sexuality and marriage was not only pursued through ‘negative’ eugenics but also through educational policies targeted at young adults and youth. Switzerland serves as a useful case to explore a general idea, namely the limitations for eugenicists of exploiting the concept of a rational subject in order to achieve (...) their ends. Practices of ‘positive eugenics’ crucially hinged on the utilitarian principle of rationality underpinning positive eugenics which this paper seeks to elaborate. Eugenicists devised tools to deal efficiently with social problems on a collective as well as an individual basis by deploying technologies of government which conceived individuals to be members of a population who were each held responsible for the generation of healthy future generations. As a form of ‘sustaining, multiplying and ordering life’ eugenics thus relied on the premise that its ideas would be adopted through an appeal to rationality and, where this was insufficient, through a series of coercive measures. Relying on conviction and education about the merits of eugenics, however, posed particular problems to positive eugenic thinking and practice. (shrink)