The four sections of the book deal in succession with Marshall’s key ideas on the subject, the wider context of his thought in which they are to be read, their later development by some of his pupils, and their revival in contemporary economics. The first and last sections work together to illustrate the evolutionary focus of Marshall’s research program and to identify its affinity with modern industrial economics; the second explicates the social assumptions within which the Marshallian paradigm was embedded, in particular those relating to the various relationships that exist between individuals and wider groups; while the third traces the development of Marshall’s views by some of his pupils.