In the West two heresies contributed to the Church's develop ment as we are studying it. Donatism focussed attention on the Church's very organisation and on her Sacraments, whereby she fulfills her work of sanctification. Its refutation,—though here the State played a more beneficent part—brought out very clearly the essential unity of the Church under the authority of the Pope.
Then the Pelagian and kindred controversies caused the better understanding of the life of grace within the soul to foster which the Church was founded. Thus these two heresies helped to clarify men's ideas on the Church as a society independent in her own sphere, and on the work that was hers to do.
Against each heresy the authority of Rome was ultimately de cisive. Though St. Athanasius, St. Cyril, St. Augustine, St. Soph ronius and others were often the most active champions against error, though on rare occasions the Pope himself was over-cautious or hesitant, ultimately the rejection of heresy was due to the leadership of Rome and to veneration for the unsullied faith of that Church.
Further the State being Christian paid great respect to the rulers of the Church. These therefore began to acquire a tem poral authority they had not before enjoyed. By actual law they were at times even temporal magistrates in their own cities. Thus as they always exercised spiritual authority, and as sometimes temporal authority was added to this, the bishops in many cities won a traditional position which when Imperial authority declined in regular efficiency made the bishops the chief rulers of their own districts. Great bishops increased the force of this tradition. The most notable example outside Rome is St. Ambrose at Milan. But it was at Rome that the development was most marked. By founding Constantinople and making it the centre of government Constantine could not destroy the tradition of centuries whereby Rome was ruler of the world. Gradually within the city the secular authority of the bishop, as a kind of Imperial representative, became paramount. He organised taxation, social works, adminis tered law, even at times entered into treaties with the barbarians who invaded Italy, acted as spokesman of the people to the Em peror and of the Emperor to the people, and occasionally even had to provide for the military protection of the city. The ma jority of the popes were as worthy of their high position as could reasonably be desired. Two however were specially eminent, St. Leo the Great (440-461) and St. Gregory the Great (59o-6o4).
As the Empire weakened under the pressure of new dangers and owing to the inevitable decay that besets all human institu tions, especially after the disappearance from 475 of a separate Western Empire, this temporal authority of the Church was gradually greatly increased. The Imperial power weakened in the
West, and the people, in their desperate needs arising from the chaos consequent upon the barbarian invasions, looked more and more for help to their immediate guides and rulers. This was pe culiarly so in Rome. The theological disputes not only widened the breach between East and West but increased the veneration of the West for the Papacy. The popes, by now manifestly the rulers of the Christian Church, joined in their persons the majesty of the Christian Kingdom and the glamour of the old Roman Im perial traditions.
From the 5th century the coming of the barbarians which af fected mainly the West, contributed greatly to the development of this ecclesiastical power. Of these barbarian tribes the ma jority were converted to Arianism. Hence they never established any alliance with the Christian Church. But the Franks who had conquered Gaul, were converted to Christianity, and from the 5th century close relations existed between them and the Holy See. The Lombards who were the last to occupy Italy were diffi cult to convert and to civilise. They did not as their predecessors the Goths had done, pay even nominal respect to the Empire. From their coming in the 6th century they were a ceaseless anxiety to the people of Italy and a danger to Roman civilisation.
Meanwhile in the East a new enemy had appeared in Moham medanism. In Africa the Mohammedans established themselves and from there advanced against Southern Italy, Spain and threat ened even Gaul. The centre of the Empire Constantinople was itself disturbed by them, and by other Eastern enemies. Thus Europe at the opening of the 8th century was in a desperate plight. Roman civilisation was not indeed destroyed, but it was weakened and in danger. A new and terrible enemy was threat ening it and threatening also the Christianity which alone could save traditional culture. The Empire was only nominally one; in the West its authority was nowhere more than nominal, and over the greater part of the West it has disappeared entirely. But at the same time the essential unity of the Church was more clearly recognised, Papal authority had been put beyond question, fundamental Christian doctrine had been clearly expressed and heresies averted. Thus, especially in the West, the one hope lay in this power of the Church; she alone exercised universal au thority, she alone was capable of transmitting to the anxious future the civilised traditions of the past, in her the glory of Christianity was joined to the splendour of Roman tradition.