During the past few years, the research of the International Center for Genetic Epistemology has dealt with causality, in its broadest sense, including every explanation of a material phenomenon, both the physical aspects of actions and their relationships to objects. The stages in the development of the understanding of causality pose much more difficult problems than the study of operations of the subjects. Because operations essentially show the general coordinations of the action, the stages of their formulation conform to an inner logic that analysis sooner or later succeeds in drawing...