1) The first meaning of "rationality" in economics is the hypothesis of "human self-interest". This is just an instrumental hypothesis. Adam Smith believes that the duality of human beings includes (a) egoism and (b) sociality. Therefore, in classical economics, sociology and economics are not antagonistic. This situation has continued to the Austrian school of Schumpeter (J.A. Schumpeter, whose masterpiece The History of Economic Analysis was originally a sociological paper written for Weber's Social and Economic Yearbook) and sociologist Weber (whose main professorship is economics). But for the most important economists at present (such as Becker and Ai Zhiren A. Al Chian, winners of the Nobel Prize in Economics), human sociality is, in the final analysis, the so-called "enlightened egoism" based on human egoism. Human egoism is the result of survival competition and social evolution. In other words, the survivors of social competition observed by economists seem to be people who act according to the "self-interest principle"; Those who don't act according to the principle of self-interest are extinct. (2) The second meaning of "rationality" in economics is "maximization principle" (which can also be expressed as "minimization principle"). This is the contribution of Marshall's Principles of Economics and the result of the "marginal revolution" initiated by the Austrian school (see Von Mises's Human Behavior). It inherits Bentham's utilitarian moral philosophy of "happiness and pain" and introduces the concept of "behavior" of positivism. The individual's pursuit of maximum happiness, or the equivalent pursuit of minimizing "pain", leads to the "maximization principle" in formal logic. This principle requires "rational choice" to expand happiness to the degree of "marginal balance": the efforts that an individual must make to increase "happiness" by a marginal amount are equal to the pain caused by such efforts. But in Marshall's view (1902, the preface to the tenth edition of Principles of Economics), the most basic and lasting forces that determine human behavior are economy and religion. This view has been forgotten by modern economics. According to p Samuelson (1947 edition), the influence of religion on human behavior can be reflected by the parameters of utility function, so that all human behaviors can be explained by the maximization of utility function in the final analysis. (3) The third meaning of "rationality" in economics is the consistency hypothesis between everyone's self-interest behavior and the self-interest behavior of others in the group. This leads to the modern concept of "social game". Therefore, economics and sociology face the same basic problems.