 Because Mill’s naturalism commits him to the principle that “[t]he laws of our rational faculty […] are only learnt by seeing the agent at work”, the investigation of scientific methodology pursued in the System of Logic takes the form of a theoretical investigation of lessons learnt from the history of successful scientific practice. It is perhaps odd, then, that Mill himself was not a historian of science of any real depth. As a matter of biographical fact, Mill’s knowledge of this topic was derived principally from secondary sources—William Whewell’s History of Inductive Science, John Herschel’s Discourse on the Study of Natural Philosophy and August Comte’s Cours de Positive Philosophie—and the sections of the System which make significant appeal to the history of science were significantly indebted to the research conducted on his behalf by Alexander Bain (Autobiography, I: 215–7, 255; Bain 1904: 137, 141). Had Mill been better acquainted with the history of actual scientific practice, it is questionable whether he would have insisted that the story of scientific progress is simply the story of the steady use of observation and induction—whether the Canons of Induction really are exhaustive of the way in which scientific investigation has enabled humans to obtain knowledge of the world. A detailed anthropological study of the history of successful scientific practice is likely to reveal the irreducible use of imaginative hypothesis-making—not to mention changing questions and ideals of the sort later highlighted by Thomas Kuhn (1962). Such was the basis for a telling historico-normative debate between Whewell and Mill—the former arguing that scientific reasoning had and should involve the creative a priori development of concepts prior to the discovery of laws, the latter claiming, as can be seen in the quote above, that observation and induction alone could track facts about the world and elicit the concepts used in science (Snyder 2006).