22 You, however, through your profound erudition, have discovered something which you think worthy to be alleged as a great objection against the Divine testimonies. For you say, “If we consider the parts comprehended in the whole world, it is a comparatively small portion in which the Christian faith is known:” either refusing to see, or pretending not to know, to how many barbarous nations the gospel has already penetrated, within a space of time so short, that not even Christ's enemies can doubt that in a little while that shall be accomplished which our Lord foretold, when, answering the question of His disciples concerning the end of the world, He said, “This gospel of the kingdom shall be preached in all the world for a witness unto all nations, and then shall the end come.” Meanwhile do all you can to proclaim and to maintain, that even though the gospel be published in Persia and India, as indeed it has been for a long time, no one who hears it can be in any degree cleansed from his sins, unless he come to Cartennæ, or to the neighbourhood of Cartennæ! If you have not expressly said this, it is evidently through fear lest men should laugh at you; and yet when you do say this, do you refuse that men should weep for you?
23. You think that you make a very acute remark when you affirm the name Catholic to mean universal, not in respect to the communion as embracing the whole world, but in respect to the observance of all Divine precepts and of all the sacraments, as if we (even accepting the position that the Church is called Catholic because it honestly holds the whole truth, of which fragments here and there are found in some heresies) rested upon the testimony of this word's signification, and not upon the promises of God, and so many indisputable testimonies of the truth itself, our demonstration of the existence of the Church of God in all nations. In fact, however, this is the whole which you attempt to make us believe, that the Rogatists alone remain worthy of the name Catholics, on the ground of their observing all the Divine precepts and all the sacraments; and that you are the only persons in whom the Son of man when He comes shall find faith. You must excuse me for saying we do not believe a word of this. For although, in order to make it possible for that faith to be found in you which the Lord said that He would not find on the earth, you may perhaps presume even to say that you are to be regarded as in heaven, not on earth, we at least have profited by the apostle's warning, wherein he has taught us that even an angel from heaven must be regarded as accursed if he were to preach to us any other gospel than that which we have received. But how can we be sure that we have indisputable testimony to Christ in the Divine Word, if we do not accept as indisputable the testimony of the same Word to the Church? For as, however ingenious the complex subtleties which one may contrive against the simple truth, and however great the mist of artful fallacies with which he may obscure it, any one who shall proclaim that Christ has not suffered, and has not risen from the dead on the third day, must be accursed— because we have learned in the truth of the gospel, “that it behooved Christ to suffer, and to rise from the dead on the third day;” — on the very same grounds must that man be accursed who shall proclaim that the Church is outside of the communion which embraces all nations: for in the next words of the same passage we learn also that repentance and remission of sins should be preached in His name among all nations, beginning at Jerusalem; and we are bound to hold firmly this rule, “If any preach any other gospel unto you than that you have received, let him be accursed.”
Source: Letters (New Advent)