For more than five centuries, Christian communities lived without a comprehensive body of written law. Thus, in the early church, canon law as a system of norms that governed the church or a large number of Christian communities, was not present. Early Christian texts share several characteristics. Their authority derived from their apostolic origins, not from ecclesiastical institutions. Although church fathers, especially John Chrysostom, did justify conciliar assemblies on the basis of Acts 15, modern scholars have concluded that the assembly described in Acts 15 at Jerusalem cannot be described as a council or synod. During the course of the fourth century, two sources of authoritative norms emerged in the Christian church: the writings of the fathers of the church and the letters of bishops, particularly the bishops of Rome. John Scholasticus' Synagoge of 50 titles is the first important collection of canon law in the East. All later Greek canonical collections were based on it.