The formative Christian period can be approached from various angles, depending on one's major interest or on what one considers central to the development of the Christian tradition in those centuries. Thus writers interested in the emergence of a mainstream institution, the church, study the period in the framework of “church history.” Those concerned with the gradual construction of normative tenets talk about “history of dogma.” Similarly, we can explore those centuries with an interest, for instance, in the history of doctrine, the history of Christian thought, the history of theology, and the history of Christian practice. Far from being mutually exclusive, all those various aspects complement each other and constitute an object that is best called “Christianity” and is most extensively dealt with in the context of history of religions or religious studies. By opting for the expression history of Christianity, I choose the formulation that is most comprehensive and least conducive to isolation from the historical and social context.
The present study of Christianity in its early history is conducted from a perspective that is not necessarily that of the church; it aims to respond to a twentieth-century detached interest in the development of Christianity as a social and religious movement, coupled with the desire to understand how and why that development took the directions it did. Given the nature of that development, readers may at times feel painfully taxed; it should then be kept in mind that challenge is also a familiar incitement to learning.
The term Christianity used in this most inclusive manner also serves to indicate that my interest goes to the many facets of the Christian movement as a historical, social, and religious process. Such an understanding of the term should not be seen as an innovation. As early as the second century, the term khristianismos itself, which became in translation Christianity, referred first of all to the concrete way of life of the Christians in opposition to that of the Jews and the Greeks; that usage is significant for its empirical connotations, akin to this book's perspective.
The historical development of Christianity can be explored through the usual scholarly means without the assumption of a faith commitment on the part of the explorers. Elements of institution, doctrine, and piety are thereby inserted into a presentation, as devoid as possible of willful partisanship, of the history and literature of the period. This approach simply reflects the migration of patristic studies out of its clerical cradle into the secular university, which has taken place particularly in the wake of the Second World War.