枢軸時代
Universal history in the Western tradition is commonly divided into three parts, viz. ancient, medieval, and modern time. The division on ancient and medieval periods is less sharp or absent in the Arabic and Asian historiographies. A synoptic view of universal history led some scholars, beginning with Karl Jaspers, to distinguish the Axial Age synchronous to "classical antiquity" of the Western tradition. Jaspers also proposed a more universal periodization—prehistory, history and planetary history. All distinguished earlier periods belong to the second period (history) which is a relatively brief transitory phase between two much longer periods.