1. It was not sufficient to prove that the rule of faith was of apostolic origin, i.e., that the Apostles had set up a rule of faith. It had further to be shown that, up to the present, the Church had always maintained it unchanged. This demonstration was all the more necessary because the heretics also claimed an apostolic origin for their _regulae_, and in different ways tried to adduce proof that they alone possessed a guarantee of inheriting the Apostles' doctrine in all its purity.[131] An historical demonstration was first attempted by the earliest of the old Catholic Fathers. They pointed to communities of whose apostolic origin there could be no doubt, and thought it could not reasonably be denied that those Churches must have preserved apostolic Christianity in a pure and incorrupt form. The proof that the Church had always held fast by apostolic Christianity depended on the agreement in doctrine between the other communities and these.[132] But Irenaeus as well as Tertullian felt that a special demonstration was needed to show that the Churches founded by the Apostles had really at all times faithfully preserved their genuine teaching. General considerations, as, for instance, the notion that Christianity would otherwise have temporarily perished, or "that one event among many is as good as none; but when one and the same feature is found among many, it is not an aberration but a tradition" ("Nullus inter multos eventus unus est ... quod apud multos unum invenitur, non est erratum sed traditum") and similar ones which Tertullian does not fail to mention, were not sufficient. But the dogmatic conception that the _ecclesiae_ (or _ecclesia_) are the abode of the Holy Spirit,[133] was incapable of making any impression on the heretics, as the correct application of this theory was the very point in question. To make their proof more precise Tertullian and Irenaeus therefore asserted that the Churches guaranteed the incorruptness of the apostolic inheritance, inasmuch as they could point to a chain of "elders," or, in other words, an "ordo episcoporum per successionem ab initio decurrens," which was a pledge that nothing false had been mixed up with it.[134] This thesis has quite as many aspects as the conception of the "Elders," e.g., disciples of the Apostles, disciples of the disciples of the Apostles, bishops. It partly preserves a historic and partly assumes a dogmatic character. The former aspect appears in the appeal made to the foundation of Churches by Apostles, and in the argument that each series of successors were faithful disciples of those before them and therefore ultimately of the Apostles themselves. But no historical consideration, no appeal to the "Elders" was capable of affording the assurance sought for. Hence even in Irenaeus the historical view of the case had clearly changed into a dogmatic one. This, however, by no means resulted merely from the controversy with the heretics, but was quite as much produced by the