These and other matters were reserved for the old courts of the shire and hundred, which the Norman kings found it advisable to encourage as a check upon their barons; for the more completely the natives and villagers were subjected to their lords, the more necessary was it for the king to maintain his hold upon their masters. For this reason William imposed the famous Salisbury oath. In France the sub-tenant was bound to follow and obey his immediate lord rather than the king. William was determined that every man's duty to the king should come first. Similarly, he separated church courts from the secular courts, in order that the former might be saved from the feudal influence of the latter; and he enforced the ecclesiastical reforms of Hildebrand, especially the prohibition of the marriage of the clergy, lest they should convert their benefices into hereditary fiefs for the benefit of their children. For the principles of heredity and primogeniture were among the strongest of feudal tendencies. Primogeniture had proved politically advantageous; and one of the best things in the Anglo-Saxon monarchy had been its avoidance of the practice, prevalent on the Continent, of kings dividing their dominions among their sons, instead of leaving all united to the eldest. But the principle of heredity, sound enough in national monarchy, was to prove very dangerous in the other spheres of politics. Office tended to become hereditary, and to be regarded as the private property of the family rather than a position of national trust, thus escaping national control and being prostituted for personal ends. The earldoms in England were so perverted; originally they were offices like the modern lords-lieutenancies of the shires; gradually they became hereditary titles. The only remedy the king had was to deprive the earls of their power, and entrust it to a nominal deputy, the sheriff. In France, the sheriff (_vice-comes_, _vicomte_) became hereditary in his turn, and a prolonged struggle over the same tendency was fought in England. Fortunately, the crown and country triumphed over the hereditary principle in this respect; the sheriff remained an official, and when viscounts were created later, in imitation of the French nobility, they received only a meaningless and comparatively innocuous title.