In primitive society the kingly and the priestly functions are commonly united; the Church and the State are one. Development leads to specialisation; the functions are divided; and the struggle for supremacy, like that between the Brahman and Kshatriya castes, becomes inevitable. In medieval Europe this struggle was peculiarly intricate, for, in the conversion of the Barbarians, a strange religion was imposed by the conquered on the conquerors; and the history of the relations between Church and State thenceforth becomes a record of the efforts of the priestly class to acquire domination and of the military class to maintain its independence. The former gradually won. It had two enormous advantages, for it virtually monopolised education and culture, and, through its democratic organisation, absorbed an undue share of the vigour and energy of successive generations by means of the career which it alone offered to those of lowly birth but lofty ambition. When Charles the Great fostered the Church as a civilising agency he was careful to preserve his mastership; but the anarchy attending the dissolution of his empire enabled the Church to assert its pretensions, as formulated in the False Decretals, and, when the slow process of enlightenment again began in the eleventh century, it had a most advantageous base of operations. With the development of scholastic theology in the twelfth century, its claims on the obedience of the faithful were reduced to a system under which the priest became the arbiter of the eternal destiny of man, a power readily transmuted into control of his worldly fortunes by the use of excommunication and interdict. During this period, moreover, the hierarchical organisation was strengthened and the claims of the Pope as the Vicar of Christ and as the supreme and irresponsible head of the Church became more firmly established through the extension of its jurisdiction, original and appellate. The first half of the thirteenth century saw the power of these agencies fully developed, when Raymond of Toulouse was humbled with fleshly arms, and John of England with spiritual weapons, and when the long rivalry of the papacy and Empire was virtually ended with the extinction of the House of Hohenstaufen. The expression of the supremacy thus won is to be found in the Gloss of Innocent IV on the Decretals and was proclaimed to the world by Boniface VIII in the bull Unam Sanctam.
This sovereignty was temporal as well as spiritual. The power of the Pope, as the earthly representative of God, was illimitable. The official theory, as expressed in the De Principum Regimine, which passes under the name of St Thomas Aquinas, declared the temporal jurisdiction of kings to be simply derived from the authority intrusted by Christ to St Peter and his successors; whence it followed that the exercise of the royal authority was subject to papal control. As Matthew of Vendome had already sung—
Papa regit reges, dominos dominatur, acerbis
Principibus stabili jure jubere jubet.
