This paper examines the purpose and intentions underlying Mill's methodological treatises. From “a priori” method to “concrete deductive method” Mill struggled for the method of social science that would be more sensitive to complexity and diversity, on which a new social science would build. Mill agreed with Comte for the need of a new science but rejected his sociology, because Mill intended to construct a new social science to guide public opinion, not to dominate it. On the other hand, Mill saw contemporary economists as narrow-minded neglecting the truth or vision that would guide human action. To write “Principles of Political Economy”, for Mill was more than to show the truth of economic phenomena by the concrete deductive method. It was to show the public the prospect of transition and its possibie, desirable way.
Along this line, Mill criticized “mercantilism” as seeing only material goods, especially money, as wealth, then extending the notion to the means that fulfill one's purpose effectively. In doing this Mill went close to the ethical-economic approach by A. K. Sen.