The task of describing the genesis of ecclesiastical dogma which I have attempted to perform in the following pages, has hitherto been proposed by very few scholars, and, properly speaking, undertaken by one only. I must therefore crave the indulgence of those acquainted with the subject for an attempt which no future historian of dogma can avoid. At first I meant to confine myself to narrower limits, but I was unable to carry out that intention, because the new arrangement of the material required a more detailed justification. Yet no one will find in the book, which presupposes the knowledge of Church history so far as it is given in the ordinary manuals, any repertory of the theological thought of Christian antiquity. The diversity of Christian ideas, or of ideas closely related to Christianity, was very great in the first centuries. For that very reason a selection was necessary; but it was required, above all, by the aim of the work. The history of dogma has to give an account, only of those doctrines of Christian writers which were authoritative in wide circles, or which furthered the advance of the development; otherwise it would become a collection of monographs, and thereby lose its proper value. I have endeavoured to subordinate everything to the aim of exhibiting the development which led to the ecclesiastical dogmas, and therefore have neither, for example, communicated the details of the gnostic systems, nor brought forward in detail the theological ideas of Clemens Romanus, Ignatius, etc. Even a history of Paulinism will be sought for in the book in vain. It is a task by itself, to trace the aftereffects of the theology of Paul in the post-Apostolic age. The History of Dogma can only furnish fragments here; for it is not consistent with its task to give an accurate account of the history of a theology the effects of which were at first very limited. It is certainly no easy matter to determine what was authoritative in wide circles at the time when dogma was first being developed, and I may confess that I have found the working out of the third chapter of the first book very difficult. But I hope that the severe limitation in the material will be of service to the subject. If the result of this limitation should be to lead students to read connectedly the manual which has grown out of my lectures, my highest wish will be gratified.