At an early point in the Economics of Imperfect Competition Mrs. Robinson assures us that her attention is to be confined to equilibrium analysis only and that she proposes to make no study of the process of inter-equilibrium adjustment. “The technique set out in this book is a technique for studying equilibrium positions. No reference is made to the effects of the passage of time. Short-period and long-period equilibria are introduced into the argument to illustrate various technical devices, but no study is made of the process of moving from one position of equilibrium to another ….” There are two alternatives open to the theorist who has adopted a methodological precept involving the complete separation of equilibrium and process analysis. It is possible, on the one hand, to follow the precept with the utmost rigour, in which case the equilibrium theory will be almost purely formal and hardly constitute an explanation of the equilibrium. Or the theorist can in practice relax his rule and introduce process propositions into the equilibrium theory. Few writers have been able fully to resign themselves to the first alternative and most have in greater or less degree followed the second. Thus there has been elaborated, largely unconsciously, a theory of the process of interequilibrium adjustment which forms an integral part of the accepted theory of the equilibrium of the firm in its usual form. It is the purpose of this paper to bring this adjustment theory explicitly to view and to determine the degree to which the validity of the equilibrium propositions is dependent upon it. It is emphasized that the discussion is restricted to the questions of internal logical consistency and formal generality of the theory.