I argue that the French sociologist Émile Durkheim (1858–1917) decided to constitute sociology, a novel field, as ‘scientific’ early in his career. He adopted evolutionized biology as then practiced as his principal model of science, but at first wavered between alternative repertoires of concepts, models, metaphors and analogies, in particular Spencerian Lamarckism and French neo-Lamarckism. I show how Durkheim came to fashion a particular deployment of the French neo-Lamarckian repertoire. The paper describes and analyzes this repertoire and explicates how it might have been available to a non-biologist. I analyze Durkheim’s very early writings between 1882 and 1892 in this context to substantiate my argument.