The doctor and psychologist Claparède founded a School of Educational Sciences in 1912 in Geneva, which he named after Jean-Jacques Rousseau. The concepts of «paedology, education, science(s) of education, child psychology, new pedagogy, functional education» were being drawn under the pen of those who designed the building needed for that, premier temple tout entier dédié à l'enfance (Letter from Claparède to Bovet, 23 November 1911). This «temple» dedicated to Rousseau, was to be located in the middle of the pedagogical and psychological landscape of the twentieth century. The relevant question is whether these terms are all equal and can coexist, interchangeably, under the sponsorship of Rousseau. Nothing is less certain if we take a look at the distortions of terminology and theoretical controversies of the early builders of the sciences of education. Our research in the archives and analyses of documents in the first decades of the twentieth century confirm this. In spite of that, beyond this observation and for the same reason as this confusion, it seems as if these opposed elements can continue cohabiting under the insignia of the restless philosopher. At the time of commemorating the 300th anniversary of Rousseau and the 250th anniversary of the publication of Émile and the Social Contract, the confusion and contradictions tenaciously persist, beyond terminology, and Rousseau is still questioned amid the school disputes. Claparède, followed by his first fellow travellers, has contributed deeply to maintaining this plebiscite claiming this finely argued affiliation, and, in spite of everything, paradoxically, according to several viewpoints. This is what we intend to demonstrate in this article, based on the voluminous archives that give accounts of the first decades of life and intellectual activity of the Rousseau Institute and terminological, epistemological and conceptual reflections of the protagonists: Claparède Ferrière and Piaget, which we wanted to reinterpret based on their references to Rousseau.