Dinamica e Ceteris Paribus in una economia Marshalliana

The paper aims to propose an innovative interpretation of the concept of ceteris paribus (CP) within Marshall’s economics. The concept of CP is analysed by means of a dynamical model in which the relevant premises and the methodological peculiarities of Marshall’s economics receive a careful mathematical treatment. The basic result of the analysis is that the CP clause may assume essentially different meanings according to (1) the kind of variable “frozen” in it and (2) the lenght of the time horizon. It is then possible to distinguish between a structural and an endogenous CP and, within the latter, between a slow and a fast CP. This double analytical distinction helps in understanding the role the CP clause plays within Marshall’s dynamic vision of the economic system: the CP concept is found to be a fundamental aspect of Marshall’s economics and not merely a symplifying analytical device. Finally, the notion of fast CP seems to suggest an extension of the standard view of the CP concept: intepreted as a dynamic on manifolds, it still reduces the degree of complexity of a system even if the variables “frozen” in it need not to be constant.