Forty years after the Crucifixion , the first reports appeared setting down Jesus's work in writing ; the Gospels were written down between shortly before 70 and shortly after 100 A.D. The first Christians had still lived in the expectation that Christ would come again very soon . The longer this event was delayed , the greater the need for an organisation of their own became , which would guarantee the faithful tradition of the message of redemption . As a result , the term 'church' , which was derived from the Greek word kuriakos meaning 'of the master' and was originally used to mean the community , was transformed . It now became an institution . The existence of the office of bishop is documented from the turn of the first century ; he was regarded as a successor to the Apostles and thus traced his authority indirectly back to Christ . He was to ensure the unity of the community . But for this purpose , Jesus's message had to be set down clearly , and as there was a considerable need for interpretation here , Christian teaching came into being , also in dispute with the pagan outside world , as apologetics , as defence not infrequently following the principle that attack is the best form of defence . A creed was formulated , about the correct form of which there was to be much discussion . Taking the reports about Jesus , an attempt was made to obtain directions for a righteous life . This included the sacrament of the Eucharist by which His memory was to be kept alive . From this developed gradually the third , now first meaning of the word church , the house of God in which the Eucharist is celebrated .

Christianity initially spread especially in the East of the Roman Empire . From the mid-third century on , Christians were persecuted and suppressed several times , but at the beginning of the fourth century Emperor Constantine promoted the new religion . For the Roman state as well as for the early Christian church , the linking together meant a turning point . The link did not result inevitably from the previous development , but was the result of Constantine's far-sightedness . Considerable corrections were required - once again both in the state and in the church -so that the unequal parts would fit together . It was already an audacious venture to link together the pompous cult of the emperor with the doctrines of charity , selflessness and non-violence . Eusebius of Caesarea developed the theological justification for the omnipotence of the emperor in his argument from analogy . The one emperor corresponded to the one God . Emperor Constantine I let himself be buried as the 13th . apostle , and alongside his throne a place remained empty for Jesus , whose deputy and co-regent he and his successors claimed to be . In contrast to the West , in the Orthodox area the Emperor retained his sacral competence ; the theory of the two powers , which Pope Gelasius developed in the 5th. century to differentiate from Constantinople's claims , did not correspond with the political reality in the East . In this lies one of the most important differences between East and West : the interpretation of the institution 'church' drifted ever further apart . Whereas in the West it was able to achieve autonomy for itself owing to the lack of a central power thus forming a counterweight to state power , in the East it remained under imperial control . Even in the modern period , the idea of the separation of Church and State has not been able to gain acceptance .

At the time when the church became a state organ , the internal development of the organisation and the teaching was far from complete . Thus , especially in the initial phase , violent controversies occurred . There was the matter , for example , of the attitude towards Christians who did not accept the fate of a martyr during a persecution , but later wanted to return to the bosom of the church . This was settled in favour of a mild position . Another point of dispute was the question whether an ordination or baptism given by such an apostate might be recognised ; here too a positive decision was taken . However , the majority of problems was caused by the differentiation from polytheism which was close to the doctrine of the Trinity of the Father , Son and Holy Ghost , and the question of how the interplay of man and God in Jesus Christ is to be understood : Was He above all a man who was inspired by God , but not Himself divine , because created by God , thus also eternal ? If the second answer had been accepted , known as Arian after the Alexandrine presbyter Areios , then for many believers the expectation of salvation , the redemption of the world , would have become doubtful . On the other hand , it was an understandable interpretation , and many endorsed it , including several emperors . The church , however , rejected this solution . At the first ecumenical council in Nicaea , the problem was solved by the differentiation into being and hypostasis , form of appearance : Christ and God are one being with two forms of appearance . Arianism still lived on for a long time , it had not been eliminated by the council's decision , thus showing that questions of faith are not to be resolved , at least not always , by decree .