Writing as a biologist and a behavioralist, Professor Hogben examines the underlying assumptions of a statistical theory. He sets down, with the clarity, brilliance, and force one expects from him, the views of the scientist who uses the formulae of statistics. He distinguishes four elements in today's theory of statistics: a calculus of error, a calculus of aggregates, a calculus of exploration, and a calculus of judgments, and he examines all of them according to their origins, contents, and validity. By tracing current conflicts of doctrine to their sources, he makes clear to the younger generation of research workers how important it is to examine and to question the credentials of principles invoked in the course of their work.