THIS COLLECTION of papers by Edward Chace Tolman, sponsored by a group of his former students and present colleagues, is not only an appropriate commemoration of his more than thirty years at the University of California but an important psychological doc-ument which shows the development of his systematic theory from its early neonatal stirrings to its later more consolidated but still-maturing phases. The development of a system has more than his-torical interest. It throws light on the very processes by which knowledge is expanded, integrated, and given meaning. Tolman's complete bibliography contains over eighty items. The problem of selection was therefore a considerable one. Since it was felt, however, that he himself was in the best position to make the most meaningful and useful selection, he was persuaded to pick out the articles which to him meant steps in the development of his theoretical system. The result can best be characterized as a “Progress Report.” Tolman is a system builder who not only theorizes, but also experiments. This means that his work is never done. He is constantly accumulating new data in his own laboratories and studying the data of other workers. He is continually adding and subtracting concepts, revising propositions, reorganizing ideas, and manipulating them creatively to see what new gestalten they might form. Tolman's now classical Purposive Behavior in Animals and Men was published in 1932. But that book was a milestone, not a capstone, for he has continued to expand, revise, and reformulate [v។