St. Augustine on the sects wishing to be called Catholic

And so, lastly, does the very name of “Catholic”, which, not without reason, amid so many heresies, the Church has thus retained; so that, though all heretics wish to be called Catholics, yet when a stranger asks where the Catholic Church meets, no heretic will venture to point to his own chapel or house.

St. Augustine (354–430): Against the Epistle of Manichaeus called Fundamental, chapter 4: Proofs of the Catholic Faith

Tertullian on disallowing Heretics’ appeal to Sacred Scripture

Our appeal [in debating with the heretics], therefore, must not be made to the Scriptures; nor must controversy be admitted on points in which victory will either be impossible, or uncertain, or not certain enough. For a resort to the Scriptures would but result in placing both parties on equal footing, whereas the natural order of procedure requires one question to be asked first, which is the only one now that should be discussed: “With whom lies that very faith to which the Scriptures belong? From what and through whom, and when, and to whom, has been handed down that rule by which men become Christians? For wherever it shall be manifest that the true Christian rule and faith shall be, there will likewise be the true Scriptures and expositions thereof, and all the Christian traditions”

Since this is the case, in order that the truth may be adjudged to belong to us, “as many as walk according to the rule,” which the church has handed down from the apostles, the apostles from Christ, and Christ from God, the reason of our position is clear, when it determines that heretics ought not to be allowed to challenge an appeal to the Scriptures, since we, without the scriptures, prove that they have nothing to do with the Scriptures. For as they are heretics, they cannot be true Christians, because it is not from Christ that they get that which they pursue of their own mere choice, and from the pursuit incur and admit the name of heretics. Thus not being Christians, they have acquired no right to the Christian Scriptures; and it may be very fairly said to them, “Who are you?”

Tertullian – On Prescription against the Heretics, 19, 37