522 THE AMERICAN ECONOMIC REVIEW SEPTEMBER which use can be made only if the decisions depending on it are left to him or are made with his active cooperation.We need to remember only how much we have to learn in any occupation after we have completed our theoretical training,how big a part of our working life we spend learning particular jobs,and how valuable an asset in all walks of life is knowledge of people,of local conditions,and special circumstances.To know of and put to use a machine not fully employed, or somebody's skill which could be better utilized,or to be aware of a surplus stock which can be drawn upon during an interruption of supplies,is socially quite as useful as the knowledge of better alterna- tive techniques.And the shipper who earns his living from using otherwise empty or half-filled journeys of tramp-steamers,or the estate agent whose whole knowledge is almost exclusively one of temporary opportunities,or the arbitragear who gains from local differences of commodity prices,are all performing eminently useful functions based on special knowledge of circumstances of the fleeting moment not known to others. It is a curious fact that this sort of knowledge should today be generally regarded with a kind of contempt,and that anyone who by such knowledge gains an advantage over somebody better equipped with theoretical or technical knowledge is thought to have acted almost disreputably.To gain an advantage from better knowledge of facilities of communication or transport is sometimes regarded as almost dis- honest,although it is quite as important that society make use of the best opportunities in this respect as in using the latest scientific discoveries.This prejudice has in a considerable measure affected the attitude toward commerce in general compared with that toward pro- duction.Even economists who regard themselves as definitely above the crude materialist fallacies of the past constantly commit the same mistake where activities directed toward the acquisition of such prac- tical knowledge are concerned-apparently because in their scheme of things all such knowledge is supposed to be "given."The common idea now seems to be that all such knowledge should as a matter of course be readily at the command of everybody,and the reproach of irra- tionality leveled against the existing economic order is frequently based on the fact that it is not so available.This view disregards the fact that the method by which such knowledge can be made as widely available as possible is precisely the problem to which we have to find an answer. IV If it is fashionable today to minimize the importance of the knowl- edge of the particular circumstances of time and place,this is closely connected with the smaller importance which is now attached to change