The Rational Expectations Hypothesis in Retrospect
考察理性预期假说与古典货币理论的关系，指出只有未预期的货币变化才影响实体经济这一核心观点在古典理论中已有体现，但两者对信息集维度的评估不同。
The rational expectations hypothesis is at the center of current debates in economic theory. The importance of this theoretical innovation has stimulated a number of studies, including analyses in the unfashionable field of the history of thought, the 1979 article by Brian Kantor being a first example. Historical investigations on the subject of rational expectations are of interest since it is held that this theory has revived the teachings of the classics, inasmuch as it provides the cornerstone of the recently developed approach known as new classical macroeconomics. The present note examines some specific aspects, as yet Pot emphasized in the literature, concerning the relationship between rational expectations and classical monetary theory. In particular, the following results will be shown: the fundamental implication of the rational expectations hypothesis, that is, that only unexpected changes in the money stock influence the real sector of the economy, is a basic tenet of classical monetary theory as well and is founded upon the very argument according to which agents efficiently use the available information in order to take account of the consequences of policy measures (Section I). This common analytical framework notwithstanding, classical analysis of the role to be assigned to the monetary authority reflects a different appraisal of the dimension of the information set (Section II).