The political conditions of Europe were thus more favorable than they had been for a long time for the development of the intellectual life. They were still far from ideal and there were many dark days in store, but the bad old times were never fully to come back. This political condition, however, was only a background for the revival of intellectual activity known as the Renaissance which distinguishes this remarkable period. This movement may perhaps be said to have begun with Petrarch, the Italian poet, philosopher, and student, who died in 1374. By the middle of the fifteenth century, however, many men had appeared in the world of letters whose names are famous for all time. These great thinkers and writers revived the study of the ancient languages, recast the study of philosophy, and even ventured to discuss the fundamentals of religion. In so doing they not only revived the ancient learning, but started a new one. New universities sprang up, among them Erfurt in 1392, Leipsic in 1409, St. Andrews, in Edinburgh, in 1411, Louvain in 1426. The revival of the study of great literature in Italy may be said to have begun about 1400. About 1450, there were many eminent Greek scholars and their enthusiasm for Greek literature had led to the revival of the philosophy of Plato. The revival of interest in the art of the ancients, classic literature, and the philosophy of Plato brought about the great advance of modern art which marked the second half of the century, Perugino, the teacher of Raphael, being born in 1446. All this intellectual activity stirred a new spirit of adventure. Just as the men whose intellectual energies had been absorbed in the petty quarrels of church and state now devoted themselves to constructive thinking, so those whose physical energies had been devoted to the constant succession of small wars of which we have spoken now gave themselves to exploration. By the middle of the century important discoveries had been made by the exploring expeditions sent out by the Portuguese prince, Henry the Navigator. The known world was to be doubled in size by the voyage of Columbus before the end of the century.