A preliminary survey is the more necessary lest the general reader fail to grant the facts of history a competent hearing and a just consideration. Unconsciously men think of the earliest Christianity as being like that which they profess. They measure the early centuries by their own. Their Church, its doctrines, forms, creeds and customs, stands as the representative of all Christianity. It seems like a “rude awakening” to ask men to believe that there is a “pagan residuum” in their faith, or in the customs of their fathers. The average Christian must pass through a broadening process, before he can justly consider such a question. Unhappily, there are too many who are unwilling to undergo such an enlargement of their religious and historical horizon as will make them competent to consider those facts which every earnest student of history must face. But the Christian who believes in the immortality of truth, and in the certainty of its triumph, will welcome all facts, even though they may modify the creed he has hitherto accepted. A writer in the _Edinburgh Review and Critical Journal_, commenting on the revised volumes of Bishop Lightfoot on _Ignatius_ and _Polycarp_, speaking of the tendency to judge the early centuries by our own, thus vitiating our conclusions, says: “The danger of such inquiries lies in the difficulty of resisting the temptation to frame pictures of an imaginary past; and the passion for transferring to the past the peculiarities of later times may be best corrected by keeping in view the total unlikeness of the first, second, or third centuries to anything which now exists in any part of the world.” Protestants in the United States are poorly prepared to consider so great a question as that which this book passes under review, because they have not carefully considered the facts touching their relations to Roman Catholicism. The Anglo-Romish controversy, in England, in the earlier part of the present century made the question of paganism in Christianity prominent for a time. But the discussion was so strongly partisan and controversial that it could not produce the best results. Truth was much obscured by the determined effort of Protestant writers to show that the pagan residuum was all in the Catholic Church; whereas the facts show that there could have been no Roman Catholic Church had not paganism first prepared the way for its development by corrupting the earliest Christianity. The facts show, with equal vividness, that Protestantism has retained much of paganism, by inheritance. Protestantism, theoretically, means the entire elimination of the pagan residuum; practically, that work is but fairly begun. It must be pushed, or the inevitable backward drift, the historical “undertow” will re-Romanize the Protestant movement. The expectations and purposes of Roman Catholicism all point towards such a result.