"In the words of Arnaldo Momigliano, the most learned and nimble interpreter of antiquity in our age: "All these civilizations display literacy, a complex political organization combining central government and local authorities, elaborate town-planning, advanced metal technology and the practice of international diplomacy. In all these civilizations there is a profound tension between political powers and intellectual movements. Everywhere one notices attempts to introduce greater purity, greater justice, greater perfection and a more universal explanation of things. New models of reality, either mystically or prophetically or rationally apprehended, are propounded as a criticism of, and alternative to, the prevailing models."