What is the teacher's role and how important is it in a child's education? Should this role include the shaping in the child's mind of the tools with which to grasp and comprehend the world? How should activities be presented so as to be easily understood by children? What are the difficulties that children encounter when resolving mathematical problems? Pedagogical methodology, the role of the educator, and the child's autonomy : these are some of the subjects that Piaget reflected on throughout his life and which remain central to educational concerns today.