Besides, men's ideas of politics, of social order, and of religion were changing rapidly, and, in a word, the whole outlook of the world was undergoing a speedy transformation. In the Middle Ages religion held the dominant position and was the guiding principle in morals, in education, in literature, and in art; but as the faith of many began to grow cold, and as the rights of Church and State began to be distinguished, secularist tendencies soon made themselves felt. Philosophy and theology were no longer to occupy the entire intellectual field, and other subjects for investigation must be found. In these circumstances what was more natural than that some should advocate a return to the classics and all that the classics enshrined? Again, the example set by the tyrants who had grasped the reins of power in the Italian States, by men like Agnello of Pisa, the Viscontis and Francesco Sforza of Milan, Ferrante of Naples, and the de' Medici of Florence, was calculated to lower the moral standard of the period, and to promote an abandonment of Christian principles of truth, and justice, and purity of life. Everywhere men became more addicted to the pursuit of sensual pleasure, of vain glory, and material comfort; and could ill brook the dominant ideas of the Middle Ages concerning the supernatural end of man, self-denial, humility, patience, and contempt for the things that minister only to man's temporal happiness. With views of this kind in the air it was not difficult to persuade them to turn to the great literary masterpieces of Pagan Rome, where they were likely to find principles and ideals more in harmony with their tastes than those set before them by the Catholic Church. The thirteenth, fourteenth, and fifteenth centuries, then, mark a period of transition from the Middle Ages to modern times. They saw a sharp struggle being waged between two ideals in politics, in education, in literature, in religion, and in morality. In this great upheaval that was characterised by a demand for unrestricted liberty of investigation, a return to the study of nature and of the natural sciences, the rise and development of national literatures, and the appearance of a new school of art, the Humanist movement or the revival of the study of the classics, the /literae humaniores/, played the fundamental part. In more senses than one it may be called the Age of the Renaissance.