28 I might spend the day in speaking to the same effect, and dry up all the streams of argument with the single Sun of the Church. But as we have already had a long discussion and the protracted controversy has wearied out the attention of our audience, I will tell you my opinion briefly and without reserve. We ought to remain in that Church which was founded by the Apostles and continues to this day. If ever you hear of any that are called Christians taking their name not from the Lord Jesus Christ, but from some other, for instance, Marcionites, Valentinians, Men of the mountain or the plain, you may be sure that you have there not the Church of Christ, but the synagogue of Antichrist. For the fact that they took their rise after the foundation of the Church is proof that they are those whose coming the Apostle foretold. And let them not flatter themselves if they think they have Scripture authority for their assertions, since the devil himself quoted Scripture, and the essence of the Scriptures is not the letter, but the meaning. Otherwise, if we follow the letter, we too can concoct a new dogma and assert that such persons as wear shoes and have two coats must not be received into the Church.
L. You must not suppose that victory rests with you only. We are both conquerors, and each of us carries off the palm—you are victorious over me, and I over my error. May I always when I argue be so fortunate as to exchange wrong opinions for better ones. I must, however, make a confession, because I best know the character of my party, and own that they are more easily conquered than convinced.
Source: The Dialogue Against the Luciferians (New Advent)