It is by now a familiar mark of sophistication to acknowledge that there can be no purely “objective” study of history, in the sense of its being entirely value-free: Objectivity is best served when the historian explicitly discloses the interpretive framework and underlying assumptions guiding the research and its outcome. Taken no further, however, this axiom can become a justification of subjective license, if not incoherence. The question remains whether, above and beyond rules of evidence and technical competence, there is a common standard of objectivity, which may be adopted by historians in forming comprehensive conceptions of an historical period and in guiding specialized inquiry as well, but which nevertheless leaves them free, even while maintaining the most rigorous criteria of logic and empirical method, to differ not only on normative matters, but also on the particular interpretations and conclusions they may draw from inquiry based on that common standard.

The principle of periodization itself offers a common standard satisfying these conditions. What general and special theories are to the meaning and indeed the very designation of facts in the physical sciences, so periodization may be to their meaning and designation in history. As referred to in this way, periodization means not the familiar device usefully invoked for narrative or connotative convenience, such as the Age of Jackson, the Gilded Age, the Progressive Era, Prosperity Decade, the New Deal, and the like.