A key theme of Chapter 1 is that Jevons’s methodology constituted a revolutionary contribution to economics. We are now in a position to demonstrate this argument in detail. Jevons believed that his methodological work, The Principles of Science: A Treatise on Logic and Scientific Method [1874, PS], was strikingly original and that it corrected many of J.S. Mill’s methodological errors. 1 The method that Jevons described for applied economics in his Principles of Science, had little in common with that of his precursors. He called for the use of new techniques of data manipulation and combination that the Classical economists, most notably Mill, rejected on principle. Such procedures entailed a break with Classical methods that opened the door for the systematic use of data and measurement in economics. 2
Historians of economics have recognized for some time that statistical procedures were available for use in social science long before they were appropriated into economic methods. 3 But the resulting puzzle of why economists resisted appropriating even simple statistical techniques, such as those designed to establish regularities in a single variable, has not yet been solved. This chapter suggests that the method of Mill erected a road-block between economists and such elementary statistical procedures. For Mill’s insistence that the economist, in application, turn attention to ‘disturbing causes’, and treat each observed outcome as a case study, precluded a role for combining observations, for measurement in economics, or for the use of Jevons’s ‘wide averages’.
A major purpose in what follows, then, shall be to demonstrate that Jevons did indeed initiate a departure from the method of J.S. Mill. 4 For while Jevons, like Mill, allowed that abstraction from causal influences was the procedure for theoretical analyses, he recommended what effectively amounted to abstraction from disturbing causes in application also. In practice, the social scientist was to ensure that disturbing causes ‘balanced’; only failing that might the scientist adjust for disturbing