边际效用之七

Let us look at the state of economic thought which prevailed on the eve of the elaboration of the modern theory of value by Carl Menger, William Stanly Jevons, and Leon Walras. Whoever wants to construct an elementary theory of value and prices must first think of utility. Nothing indeed is more plausible than to assume that things are valued according to their utility. But then a difficulty appears which presented to the older economists a problem they failed to solve. They observed that things whose "utility' is greater are valued less than other things of smaller utility. Iron is less appreciated than gold. This fact seems to be incompatible with a theory of value and prices based on the concepts of utility and use-value. The economists believed that they had to abandon such a theory and tried to explain the phenomena of value and market exchange by other theories. 讓我們來看看在孟格爾（Carl Menger）、傑逢斯（William Stanly Jevons）和瓦拉斯（Leon Walras）提出現代價値論前夕的經濟思想的情況。凡是想建立一種價値與價格基本理論的人，一定會首先想到效用。「事物是按照它們的效用而被估値的」，這個說法是最能叫人信服的。但在當時，卻有一個困難爲老輩的經濟學家所未曾解決。他們看到一些「效用」較大的東西，比「效用」較小的東西反而估値較低。「鐵」比「金」較不重視。這種事實似乎不符合基於效用與使用價値兩概念的價値與價格理論。於是經濟學家認爲，他們不得不放棄這樣的理論，試圖用其他理論來解釋和市場交換那些現象。 Only late did the economists discover that the apparent paradox was the outcome of a vicious formulation of the problem involved. The valuations and choices that result in the exchange ratios of the market do not decide between gold and iron. Acting man is not in a position in which he must choose between all the gold and all the iron. He chooses at a definite time and place under definite conditions between a strictly limited quantity of gold and a strictly limited quantity of iron. His decision in choosing between 100 ounces of gold and 100 tons of iron does not depend at all on the decision he would make if he were in the highly improbable situation of choosing between all the gold and all the iron. What counts alone for his actual choice is whether under existing conditions he considers the direct or indirect satisfaction which 100 ounces of gold could give him as greater or smaller than the direct or indirect satisfaction he could derive from 100 tons of iron. He does not express an academic or philosophical judgment concerning the "absolute" value of gold and of iron; he does not determine whether gold or iron is more important for mankind; he does not perorate as an author of books on the philosophy of history or on ethical principles. He simply chooses between two satisfactions both of which he cannot have together. [p. 122] 到後來，經濟學家們才發現，這個表面上的矛盾是由於把問題講錯了。表現於市場交換率的估値和選擇，並不在「金」和「鐵」之間抉擇其一。行爲人不能夠在「所有的」金與「所有的」鐵之間作選擇。他是在一定時間、一定地點，在確定數量的金和確定數量的鐵之間作選擇。他在100盎司的金和100噸的鐵之間所作的選擇決定，與他在一個絕對不可能的假設下，在所有的金與所有的鐵之間所作的選擇決定，完全不相干。與他實際上的決定有關的，只是在實際情況下，他要考慮100盎司金所能給他的滿足（直接的和間接的）是大於或小於100噸鐵所能給他的滿足。他並不對於金和鐵的「絕對」價値作一學究式的或哲學式的判斷；他也不決定對於人類更重要的是金還是鐵；他不會像歷史哲學家或倫理學家著書立說時那樣下結論。他只是在兩個不能兼而有之的滿足之間作選擇。 To prefer and to set aside and the choices and decisions in which they result are not acts of measurement. Action does not measure utility or value; it chooses between alternatives. There is no abstract problem of total utility or total value.[1] There is no ratiocinative operation which could lead from the valuation of a definite quantity or number of things to the determination of the value of a greater or smaller quantity or number. There is no means of calculating the total value of a supply if only the values of its parts are known. There is no means of establishing the value of a part of a supply if only the value of the total supply is known. There are in the sphere of values and valuations no arithmetical operations; there is no such thing as a calculation of values. The valuation of the total stock of two things can differ from the valuation of parts of these stocks. An isolated man owning seven cows and seven horses may value one horse higher than one cow and may, when faced with the alternative, prefer to give up one cow rather than one horse. But at the same time the same man, when faced with the alternative of choosing between his whole supply of horses and his whole supply of cows, may prefer to keep the cows and to give up the horses. The concepts of total utility and total value are meaningless if not applied to a situation in which people must choose between total supplies. The question whether gold as such and iron as such is more useful and valuable is reasonable only with regard to a situation in which mankind or an isolated part of mankind must choose between all the gold and all the iron available. 取捨、選擇以及決定（所导致的结果），都不是衡量的行爲。行爲並不衡量效用或價値：它只在不可兼得的事物之間作選擇。沒有什麼總效用或總價値（total utility or total value）這樣的抽象問題[1]。我們不能從一定數量的事物的估値推論到較多或較少數量事物的價値。如果只知道部份存量的價値，我們沒有方法可以計算總存量的價値。（漏译：如果只知道总存量的價値，我們沒有方法可以計算部分存量的價値。）在價値和估値的領域內沒有算術的運算；沒有價値計算這樣的事情。對於兩物的全部存量估値，會不同於部份存量的估値。例如一位孤立的人，有七條牛和七匹馬，他對一匹馬的估値可能高於對一條牛的估値，因而當他必須選擇其一的時候，他寧可放棄一條牛而不放棄一匹馬。但在同時同一個人，如果他必須在馬的全部存量和牛的全部存量之間作一選擇，他也許願意保有那些牛而放棄那些馬。總效用與總價値這種概念，如果不是用在人們必須在幾種總存量之間選擇其一的場合，是沒有意義的。金的本身與鐵的本身究竟那個更有用、更有價値這個問題的提出，只有在一種場合是合理的，即：人類或孤立的那部份人類，必須在「所有的」金與「所有的」鐵之間來選擇其一的場合。 ================================================================================== 这几段比较简单，是解决古典经济学一直未解决的一个难题。对于明白一些主观价值论的人们，理解起来应该都没有问题。 链接下面 http://www.douban.com/group/topic/23429592/