The purpose of this book is to draw a brief but accurate picure of the church in its historical reality and ambiguity from the standpoint of the original revelation in Jesus and in the reception of that revelation by his first followers. It is precisely the normative character of the church of the earliest days which makes church history different from purely secular history and it is also this factor which should keep the church historian honest. In this book, I have, more than is usually the case, emphasized the role of theology in the life of the church. The study of church history makes makes its clear that theology is not an esoteric pastime for a clerical leisure class but an extremely important factor in explaining the growth and change of the church from the beginning. Since theology is the attempt to make accurate use of human language in order to speak about God, it would be very surprising if this were not the case. The author has attempted to present these events in a way that will be helpful to us in making informed judgments about the unique tasks we face today. For ultimately, this is the purpose of church history as a theological discipline. Christians are called by God's word, by external messages, to confront an ever-changing world, and to evaluate its challenges, possibilities, and dangers. In the past, Christians have accepted some of these challenges and rejected others; they have seized some possibilities and let others pass them by; they have seen and been alert to some dangers, and they have turned a blind eye and fallen prey to others. Perhaps more than in any other area of life, this old adage holds true in church history: those who do not understand the past are condemned to repeat it.