But the great international center of feudalism was the Roman Catholic Church. It united the whole of feudalized Western Europe, in spite of all internal wars, into one grand political system, opposed as much to the schismatic Greeks as to the Mohammedian countries. It surrounded feudal institutions with the halo of divine consecration. It had organized its own hierarchy on the feudal model, and, lastly, it was itself by far the most powerful feudal lord, holding, as it did, fully one-third of the soil of the Catholic world. Before profane feudalism could be successively attacked in each country and in detail, this, its sacred central organization, had to be destroyed. Moreover, parallel with the rise of the middle-class went on the great revival of science; astronomy, mechanics, physics, anatomy, physiology, were again cultivated. And the bourgeoisie, for the development of its industrial production, required a science which ascertained the physical properties of natural objects and the modes of action of the forces of Nature. Now up to then science had but been the humble handmaid of the Church, had not been allowed to overstep the limits set by faith, and for that reason had been no science at all. Science rebelled against the Church; the bourgeoisie could not do without science, and, therefore, had to join in the rebellion. The above, though touching but two of the points where the rising middle-class was bound to come into collision with the established religion, will be sufficient to show, first, that the class most directly interested in the struggle against the pretensions of the Roman Church was the bourgeoisie; and second, that every struggle against feudalism, at that time, had to take on a religious disguise, had to be directed against the Church in the first instance. But if the universities and the traders of the cities started the cry, it was sure to find, and did find, a strong echo in the masses of the country people, the peasants, who everywhere had to struggle for their very existence with their feudal lords, spiritual and temporal. The long fight of the bourgeoisie against feudalism culminated in three great, decisive battles.