07 金融经济学第七讲

《金融经济学》第七讲 8
维特根斯坦 (Ludwig Wittgenstein, 1889-1951)
"My propositions are elucidatory in this way: he who understands me finally recognizes them as senseless, when he has climbed out through them, on them, over them. (He must so to speak throw away the ladder, after he has climbed up on it.) He must surmount these propositions; then he sees the world rightly." (Ludwig Wittgenstein, Tractatus LogicoPhilosophicus, 1921: Prop. 6.54)
自从遍于这个世界的芸芸众生和白面书生，都正 在宣称看不见的手的有益交互作用而不知所云以 来，我所考虑的 Arrow-Debreu 均衡的这一负面作 用，是对这一点的几乎充分的辩护。 －《论经济学中的均衡概念》 (1974)
《金融经济学》第七讲 13
Gerard Debreu (1921-2004)
对经济命题可应用范围估计过高的最好防 范是仔细地说清楚它们所依靠的前提。精确、严 格地陈述前提和证明，能使我们对已经展开的命 题延伸的信念不至于头脑发热。 －《关于经济科学现状的三篇随笔》(1957)
《金融经济学》第七讲 11
Kenneth J. Arrow and Frank H. Hahn
"In attempting to answer the question `Could it be true?', we learn a good deal about why it might not be true." (Kenneth J. Arrow and Frank H. Hahn, General Competitive Analysis, 1971: p.vii)
《金融经济学》第七讲 7
熊彼德 (Joseph Schumpeter, 1883-1950)
按照我的意见，瓦尔拉斯是所有经济学 家中最伟大的一位。他的经济均衡的体系， 正是一种把“革命”创造性的品质与经典综 合的品质统一在一起的体系，是仅有的能与 理论物理的成就并肩而立的一位经济学家的 工作。与它相比，当时 (和以后) 的理论著作 的大多数，尽管有其自身的价值，尽管主观 上是开创性的，但看起来像是大客轮旁的小 船，像是要把握瓦尔拉斯真理的某些特殊方 面的不充分的尝试。 －经济分析史 (1954)
第七讲 一般经济均衡 与资产定价
第六讲要点
Von Neumann-Morgenstein 期望效用函数用一个数字 指标来刻画人们在不确定环境下的决策。它由一个 抽象公理体系来确定，完全脱离现实。但它是一种 “经济学表达理论的方式”。 用“递增凹函数”当期望效用函数至今仍是研究主 流。由此导出 Arrow-Pratt 风险厌恶度量、随机占优 等常用概念。 联系具体经济环境中的人的心理和行为，期望效用 函数肯定常有偏差。但一般来说，任何抽象架构都 会有局限。“框架效应” 永远难免。
《金融经济学》第七讲 14
"Being denied a sufficiently secure experimental base, economic theory has to adhere to the rules of logical discourse and must renounce the facility of internal inconsistency. A deductive structure that tolerates a contradiction does so under the penalty of being useless since any statement can be derived flawlessly and immediately from that contradiction. In its mathematical form, economic theory is open to an efficient scrutiny for logical errors." (Gerard Debreu, "The Mathematization of Economic Theory", American Economic Review, 1991)
Content without method ends in sentimental chaos; Method without content in sophistry; Material without form is a dead-weight of fact; Form without material is a spinning of cobwebs.
sufficient justification for it, since practical men and ill trained theorists everywhere in the world who do not understand what they are claiming to be the case when they claim a beneficient and coherent role for the invisible hand" (Frank H. Hahn, On the Notion of Equlibrium in Economics, 1974: 52).
"Walras is in my opinion the greatest of all economists. His system of economic equilibrium, uniting, as it does, the quality of a "revolutionary" creativeness with the quality of classic synthesis, is the only work by an economist that will stand comparison with the achievements of theoretical physics. Compared with it, most of the theoretical writings of that period and beyond - however valuable in themselves and however original subjectively, look like boats beside a liner, like inadequate attempts to catch some particular aspects of Walrasian truth." (J. A. Schumpeter, History of Economic Analysis, 1954: p.827)
《金融经济学》第七讲
9
维特根斯坦 (Ludwig Wittgenstein, 1889-1951)
我的命题是以这样的方式来阐 明的：理解我的人，如果他曾经攀 登过它们，登上它们，超越它们， 最终把它们辨认为毫无意义。(在他 曾经登上它以后，他必定如此，而 说扔开梯子。) 他必须战胜这些命题；然后他 才正确地看世界。
《金融经济学》第七讲 2
意义
在经济学上，它是惟一的对经济整体提出的 理论。 在方法论上，它是“静态均衡”的彻底的公 理化陈述。 作为一种抽象架构，它同样有其种种局限。
《金融经济学》第七讲
4
歌德
(Johann Wolfgang von Goethe, 1749-1832)
经济理论公理化的好处已经数不 胜数。完全清晰地作出理论假定使得 对它所应用的特殊情况的范围有更可 靠的判断。
－Debreu 诺贝尔奖演说 (1983)
"The benefits of the axiomatization of economic theory have been numerous. Making the assumptions of a theory entirely explicit permits a sounder judgement about the extent to which it applies to a particular situation." (Gerard Debreu, "Economic Theory in a Mathematical Mode", American Economic Review, 1984)
The principal subject of our study is economic equilibrium. We shall see shortly that this equilibrium results from the opposition between men's tastes and the obstacles to satisfying them. Our study includes, then, three distinct parts: 1° the study of tastes; 2° the study of obstacles; 3° the study of the way in which these two elements combine to reach equilibrium.“ (Vilfredo Pareto, Manual of Political Economy, 1906: p.106)