This phase of human evolution, as may be seen, was radically different from that already considered, arising from the development of sacerdotal influence and priestly power. They worked together, no doubt. The establishment of the great primitive empires, as a peaceful process, was greatly complicated by war, which tended steadily to increase the temporal power of the ruler and enable him in time to control by the sword alone. But it is interesting to find that long after the old system was practically overthrown its shadow still lay upon the nations. The powerful war monarchs of Assyria led their armies to conquest in the name of the national deity, whose vicegerents they claimed to be. The autocratic emperors of Rome went so far as to claim in some cases to be gods themselves. Even in modern Russia some of this dignity pertains to the emperor, as the supreme head of the national church. Old ideas are proverbially hard to kill. But the mission of the priesthood by no means stopped here. The priests rose to influence as the teachers as well as the leaders of the people. The members of this class, set aside from manual occupations, and devoted to thought upon the relations of man to the divine, played an important part in the development of the human mind. As a result of their speculative activity of thought the old religious systems sank into the background; the simple worship of primitive times was overshadowed by intricate mythological systems, splendid in worship and creed; cosmogonies and philosophies were devised; and human thought, once fairly set loose in this field, went on with great energy and imaginative fervor. Literature arose as a result of this activity of thought. It took at first the form of hymns, speculative essays, magical formulas, dogmas, ordinances of worship, etc. By degrees it grew more secular in form, until in the end secular literature arose. This was greatly stimulated by the conditions of inequality arising from war. In the same manner as the reward for merit in invention stimulated men to activity in the mechanical arts, so the hope of reward for literary production stirred up men to the composing of poems, histories, and other works of thought. In both directions, physical and mental, men were stimulated to the most active exertions by the conditions of inequality in wealth and power, and the consequent desire to obtain a share of the money lavished by the rich and the authority similarly lavished by the powerful.