This essay offers a new approach to a familiar topic. It is an attempt to clarify certain early Christian ideas about society by defining the particular social institutions that are presupposed, and showing how the behavior of the Christians was related to them. At first it was thought that an analysis of the social stratification of the Christian groups would suffice, but on investigation the conception of society as a series of strata seemed increasingly anachronistic. Instead it became apparent that the contemporary writers were thinking in terms of a series of overlapping but not systematically related circles. The description of these circles occupies the main body of the essay. - Preface.