In his classic book, Human Nature in Politics, published in 1908, Graham Wallas said: “We must aim at finding as many relevant and measurable facts about human nature as possible, and we must attempt to make all of them serviceable in political reasoning.” While the point of view which Wallas expressed at that time has by no means been universally accepted, and is today challenged by men like Charles A. Beard, certain steps have been taken toward its recognition.
Wallas was particularly impressed by the successful use of quantitative methods made by the economists, and well he might be. To mention a single case, the work of F. Y. Edgeworth, in the measurement of utility, the algebraical or diagrammatic determination of economic equilibriums, and the application of the theory of probability to sampling and in the measurement of economic value or index numbers, showed the trend of the times in economics. The twentieth century has marked an acceleration of this trend. Political scientists have not only lagged far behind the economists in the use of statistics, but they have shown important resistance in some sections to following in this general direction. What is the explanation of this situation?