This paper examines the relationship between the puericulture of Adolphe Pinard and Léon Bourgeois’ solidarism. In an attempt to create a progressive and humanistic form of eugenics, Pinard links the science he was developing with the imperatives of social justice advocated by Bourgeois. This results in, on the one hand, the subordination of puericulture to principles of equality and fundamental rights for all individuals and, on the other, the idea of the need for a (...) biological enhancement of the population as a condition for the extension of liberty and solidarity. The first part of the article establishes a connection between the two authors through the neo-Lamarckian paradigm which they spoused, and details the how and the why of solidarism. A second part examines the nature of the assimilation of the “religion of humanity” into solidarity, which entails both the defence of love at a collective level and the sanctity of those deemed “abnormal”. A final part describes the solidarist-inspired levers envisaged by Pinard for preventing the degeneration of humanity. They are based on a redefinition of the criteria used to determine the value of the social function of the individual and have an impact on the family, on the one hand, and eugenic women on the other. (shrink)