The theoretical foundations of Québec's early prevention programs question the researchers and fieldworkers' normative choices and raise the question of the possible impacts on the democratic nature of intervention practices directed towards underprivileged families. The article discusses an hypothesis according to which, the normative postulates of the theoretical foundations of early prevention programs, postulates drawn mostly from the ecology of human development, are used to construct a scientistic fallacy : the control of human development through a technical and instrumental knowledge of behavioral or interactive patterns. Intervention's objectives, like the prevention of the intergenerational reproduction of teenagers' adaptation problems, must be examined from a critical perspective to foster a meaningful debate on the ethical foundations and on the political consequences of these programs implementation. The article concludes with a description of these consequences for mothers, young persons, community-based organizations' practices, public institutions' practices and on the more general democratic context.