凱恩斯的宏觀經濟學：學術評價（2）
蔣聞銘
再論凱恩斯理論的曆史背景
經濟學作為一門學科，本質上屬於社會科學，其性質與自然科學和數學有著根本性的不同。如果在數學證明中發現了上述那樣的錯誤論證，這個證明會立即崩潰。同樣，在物理學中，隻要存在一個可以重複的現象與某一理論的預測相矛盾，該理論就會被判定為錯誤。
然而，在社會科學中，用來支撐某一理論的具體論證是否嚴密，往往隻是次要問題。錯誤的技術性論證固然會損害一個理論的聲望，但並不會因此直接否定其所主張的命題。以“上帝是否存在”為例，曆史上曾有許多“證明”，它們或多或少都包含邏輯錯誤。然而，對這些證明的駁斥，並不能真正解決這一問題——至少對虔誠的信徒而言並非如此。
具有重大影響力的社會理論，從來都不是建立在純粹學術化的論證或冷冰冰的數學邏輯之上的。它們往往源自充滿激情的思想者內心深處的驅動力，是對其時代重大問題的一種回應。要真正理解一種社會理論，不在於對其進行技術性的分析解剖，而在於理解：為什麽某些在現代人看來顯得荒謬的觀點，會被一位卓越的思想家視為永恒真理的一部分。
凱恩斯的理論產生於一個對自由資本主義在實踐和理論上都極為不利的時代。建立在自由貿易和私有製原則之上的既有經濟秩序，已經被一場大蕭條嚴重破壞。按照當時主流經濟理論——以供求規律為基礎——人們原本預期經濟會自行複蘇，但現實卻是經濟狀況持續惡化。長期居高不下的失業率引發了政治與社會的動蕩。
共產黨人和法西斯主義者將這一切歸咎於自由市場製度本身。他們宣稱，自由企業的短視以及資本家的無節製貪婪，導致了不負責任的經濟決策，把世界推入了混亂之中；更糟的是，在現有的經濟與政治框架下，根本沒有出路。他們主張，唯一的辦法就是推翻自由資本主義的基礎，建立一種新的社會與經濟秩序。他們所提供的這種“新秩序”，不過是用自由去交換麵包。然而，對於半饑半飽的人來說，麵包往往比自由更為迫切。於是，在世界各地，民主製度開始讓位於專製統治——無論是共產主義還是法西斯主義——全球自由資本主義體係似乎已瀕臨崩潰的邊緣。
而那些具有自由主義精神的人，則清醒地意識到專製政權潛在的危險，因而拒絕了共產主義與法西斯主義的主張。他們試圖在現有製度之內尋找解決危機的辦法。顯而易見，要避免既有社會秩序的全麵崩潰，必須消除高失業這一禍患。如果私人部門不願投資，那麽政府就必須出手投資。於是，“新政”（New Deal）應運而生。然而，行動者仍然需要一套理論作為支撐，而這一理論正是由凱恩斯提供的。
Keynes's Theory-- Historic Background
Economics as an academic subject is essentially a subject of social science, the nature of which is entirely different from that of physical science and mathematics. If one finds a faulty argument as described in the above in a mathematical proof, the proof would immediately collapse. Likewise, a physics theory would be deemed as false if there exists a single repeatable phenomenon that is contradicting to its predictions. In social science, on the other hand, the correctness of a detailed argument employed to support a theory is usually of secondary importance. Incorrect technical argument undoubtedly would taint the prestige of a theory, but would not invalidate the advocated proposition. Taking the issue on the existence of the GOD as an example. There had been many proofs offered, each committed logic mistakes of one kind or another. However, invalidating these proofs never settles the issue at hand, not at least to true believers. Social theory of great influence are never based on academically oriented arguments and cold mathematical logic. They are usually created by the inner drives of passionate souls in providing answers to burning questions of their times. To properly understand a social theory is not to dissect the technical analysis offered, but to understand why a theory, in occasions sounds ridiculous to a modern mind, could be regarded as part of eternal truth by a superb mind.
Keynes's theory emerged at a time that is particularly troubling to free capitalism both in practice and in theory. Established economic order based on the principle of free trade and private ownership had been severely damaged by a great depression. Instead of a recovery, anticipated by the prevailing economics theory of that time based on the law of supply and demand, economic condition continued to deteriorate. Long lasting high unemployment rate led to political and social turmoil. The communists and fascists blamed the fundamentals of the free market system. They claimed that the short-sight of the free enterprise and the unbounded greediness of the capitalists had led to irresponsible economic decisions that had throw the world into a terrible mess, and worse, there is actually no way out under the existing economic and political framework. The only way, they advocated, is to overthrow the fundamentals of the free capitalism to establish a new social and economic order. Unfortunately, the alternative new order they offered was nothing but trading your freedom for bread. Half empty stomach, however, needed bread more urgently than freedom. All around the world, democracy started to give way to dictatorship -- to Communism and Fascism, and the global free capitalist system appeared to be at the verge of collapsing.
Liberal souls, acutely aware of the potential evil of a dictatorship government, rejected the communist and fascist preach. They tried to find a way inside of the existing system to fix the mess. It was obvious that to avoid a total collapse of the existing social order, the evil of high unemployment must be dispelled. If private party is unwilling, then government must invest. Thus came the New Deal. People of action, however, needed a theory, which is then offered by Keynes, to back them up.
The gist of his "general theory" is rather straight forward. In order to restore employment to avoid a total collapse of the existing social and economic system, somebody must hire people to work. This is to say that somebody must invest. However, in an bad economical and unstable political environment, in which there appeared no incentives to invest, (marginal efficiency of capital is close to zero, in his word), private, free capital would shy away. In this case, the free market lost its capacity to self-adjust. Easy money policy of the monetary authority was destined to fail--seeing no incentives to invest, the unwilling private investors would rather buy government bonds. The latter, however, presented an opportunity for the government to raise the existing economic resources from private party and to use the money raised to hire people to work. In this sense, any job is better than no job, for anything, even digging useless holes in desert, helps to ease the social pressure of unemployment. With unemployment situation improved, and social order would be more or less restored, and private investors would have more incentives to hire more people to create a true economic recovery.
Ironically, free capitalist system was saved neither by the New Deal nor by Keynesian theory. It was saved by the second world war: hence in a sense it was saved by the actions of its mortal enemy. Emergency war time power enabled the government to expand its authority into economic arena in an unparalleled way, and the evil of unemployment was cured almost over night: though people were actually hired to do jobs that are much worse than digging useless holes on desert: they are now hired for the purpose of killing each other. In war time, the traditional influence of the private enterprise over the government, together with their short-sight and greediness,
started to wane, make it possible for the government to introduce mild social and economic reforms in post war time, among which the most important were mild wealth re-distribution through labor law. Recovered from the death bed, the free capitalism not only survived, but also re-energized, entering an age of long prosperity and unprecedented growth. There had been only two major setbacks: the super-inflation of the 70th and the market crush of 2008, both are much less severe than the great depression.
