The fourth century is the most vital turning point of ancient Christianity, because many changes took place at that period regarding the future fate of the Church. First of all, the century begins with the ‘Great Persecution’ of the Diocletianus, which intermittently continued for about a decade. Secondly, the end of this persecution brought not only the conversion of Constantinus but also the councils of bishops to heal the wounds of the persecution. In spite of the fact that there were very sharp differences in the western churches, the conversion of a Roman emperor naturally resulted in the integration of the church and state in the East, and this was mostly achieved at the church councils. Thirdly, it was also a period, in which the most serious theological dispute, the Arian controversy, broke out and consequently led to a traffic of church councils to establish a generally accepted doctrinal definition in the middle years of the century. The Arian controversy was a major problem that the emperors had to deal with. However, there were also localized ecclesiastical problems, emerged from ascetic, theological and political concerns, such as local interpretations of the Arianism, the Meletians in Egypt, the Anatolian asceticism of Eusebius of Sebaste, and the Monophysite teachings of the Syrian theologian Apollinarius, which was condemned at the second ecumenical council of Constantinopolis in 381. In fact, the first two ecumenical councils of the early church took place in the fourth century and their decisions and definitions of the Creed are still used by present day Christians to declare their own faith.