lovejoy on the history of ideas as “analytic chemistry.”
By the history of ideas I mean something at once more specific and less restricted than the history of philosophy. It is differentiated primarily by the character of the units with which it concerns itself. Though it deals in great part with the same material as the other branches of the history of thought and depends greatly upon their prior labors, it divides that material in a special way, brings the parts of it into new groupings and relations, views it from the standpoint of a distinctive purpose. Its initial procedure may be said—though the parallel has its dangers—to be somewhat analogous to that of analytic chemistry. In dealing with the history of any philosophical doctrines, for example, it cuts into the hard-and-fast individual systems and, for its own purposes, breaks them up into their component elements, into what may be called their unit-ideas. The total body of doctrine of any philosopher or school is almost always a complex and heterogeneous aggregate—and often in ways which the philosopher himself does not suspect. It is not only a compound but an unstable compound, though, age after age, each new philosopher usually forgets this melancholy truth. One of the results of the quest of the unit-ideas in such a compound is, I think, bound to be a livelier sense of the fact that most philosophic systems are original or distinctive rather in their patterns than in their components.
— Arthur O. Lovejoy, The Great Chain of Being: A Study of the History of an Idea