John Stuart Mill underwent a mental crisis in the 1820s. He emerged from it, argues Fred Wilson, with a new understanding of the notion of introspective analysis more dequare as an empirical method than the sort of analysis that had been used by earlier utilitarian thinkiers such as Bentham and James Mill. Wilson's study places Mill's innovations in the context of earlier work in ethics and perception and of subsequent developments in the history of psychology. He shows the significance of these topics with which Mill was concerned.The more adequate notion of introspective analysis enabled the younger Mill to reply to criticisms of various empiricist and utilitarian positions cencering the analysis of relations, the nature of our percievings of physical objects, the status of science of economics, and the nature of the utilitarian principle itself.Mill was thus able to reject the quantitative hedonism of his predecessors and to introduce qualitative hedonism in its place. Wilson suggest that the long tradition that views Mill's qualitative hedonism as inconsistent is mistaken, as area a variety of criticisms of his work in the psychology of perception and the philosophy of economics. A better grasp of the background of Mill's views of psychology and the philosophy of psychology easily shows the critics to be mistaken.