Description: Claparède and Vygotsky: both are intellectuals with a wide range knowledge. Both are scientists constructing a theory of the psychological functioning. Both contribute to the construction of a "new pedagogy" (Claparède) or of "pedology" (Vygotsky). Both work until the thirties of the 20th century. Both are heavily engaged in school reforms in their respective country, contributing to a New Education. The role of knowledge in their conception of education seems nonetheless strongly contrasted. We will test this hypothesis in asking three interrelated questions: - Given the general context of strong reform movements, how do Claparède and Vygotsky define the role knowledge has to play for the profession of education ? How is teacher education conceived of and what is the function of research for education? - What kind of knowledge base do the two actors elaborate ? How is education and teaching theoretically conceived from the point of view or their form and their function for development? - What is in their view the role that knowledge has for the persons to be educated, more particularly for students in school? In order to answer these questions the collected works of both authors are at our disposal (see the bibliographies of Trombetta, 1976, for Claparède and of Shalevitch, 1974, for Vygotsky). For answering the first, we will explore the texts in which both authors discuss the institutional question of education of educators and more generally the question of the relationship between theory and practice (for instance in the introductory chapters of Psychologie de l'enfant et pédagogie experimental by Claparède and in La signification de la crise de la psychologie and texts on defectology by Vygotsky). The second question will be treated in comparing two significant texts on child development Le développement de l'enfant by Claparède et Foundations of paedology where Vyogtsky defines this latter as science of development. The third question will be explored through texts of Claparède and Vygotsky on different school subjects, like reading, grammar, writing, foreign languages and drawing, and through the comparison of their respective analysis of Tolstoi's contribution to the conception of school and the role of knowledge.