Ideology, more conventionally called theory, is essential if historians are to select and integrate new material. And idiosyncrasy in the interests and backgrounds of historians can often be the source of the re-vision so essential for challenging earlier historical narratives. It reflects our priorities, our values, and our understanding of the forces of continuity and change. Yet periodization is also subject to practical constraints. For pedagogical reasons, world historians must seek reasonable symmetry between major historical eras despite huge discrepancies in the availability of historical data for separate time periods and for different areas of the world.
Political issues arise in periodization.
Although the article attempts to demonstrate how comprehensive theories of change can facilitate the formulation of world history periodization, it does not minimize the difficulty of developing a universally operative organic theory of change. It examines several theoretical orientations, but principal attention is given to world-systems analysis, the most fully refined and well articulated body of theory currently commended as a vehicle for structuring world history. Acknowledging that no body of theory currently achieves a satisfactory universal integration of world history and that this situation may prevail in the future, the author recommends, for the present, an eclectic periodization of four epochs divided at roughly 1000 B.C.E., 400-600 C.E., and circa.