Now it is evident that the term “Christianity” used as a point of view, a mere mental attitude, would include such a man, and it is equally evident that we have only to imagine him to see that he had nothing to do with the Christian _religion_ of that day. For the Christian religion (then as now) was a thing, not a theory. It was expressed in what I have called an organism, and that organism was the Catholic Church. The reader may here object: “But surely there was heresy after heresy and thousands of men were at any moment claiming the name of Christian whom the orthodox Church rejected. Nay, some suffered martyrdom rather than relinquish the name.” True; but the very existence of such sects should be enough to prove the point at issue. These sects arose precisely because within the Catholic Church (1) exact doctrine, (2) unbroken tradition, and (3) absolute unity, were, all three, regarded as the necessary marks of the institution. The heresies arose one after another, from the action of men who were prepared to define yet more punctiliously what the truth might be, and to claim with yet more particular insistence the possession of living tradition and the right to be regarded as the centre of unity. No heresy pretended that the truth was vague and indefinite. The whole gist and meaning of a heresy was that it, the heresy, or he, the heresiarch, was prepared to make doctrine yet more sharp, and to assert his own definition. What you find in these foundational times is not the Catholic Church asserting and defining a thing and then, some time after, the heresiarch denying this definition; no heresy comes within a hundred miles of such a procedure. What happens in the early Church is that some doctrine not yet fully defined is laid down by such and such a man, that his final settlement clashes with the opinion of others, that after debate and counsel, and also authoritative statement on the part of the bishops, this man’s solution is rejected and an orthodox solution is defined. From that moment the heresiarch, if he will not fall into line with defined opinion, ceases to be in communion; and his rejection, no less than his own original insistence upon his doctrine, are in themselves proofs that both he and his judges postulate unity and definition as the two necessary marks of Catholic truth. No early heretic or no early orthodox authority dreams of saying to his opponent: “You may be right! Let us agree to differ. Let us each form his part of ‘Christian society’ and look at things from his own point of view.” The moment a question is raised it must of its nature, the early Church being what it was, be defined one way or the other. Well, then, what was this body of doctrine held by common tradition and present everywhere in the first years of the third century?