Pope Pius VI, “Inscrutabile”

"When they have spread this darkness abroad and torn religion out of men's hearts, these accursed philosophers proceed to destroy the bonds of union among men, both those which unite them to their rulers, and those which urge them to their duty. They keep proclaiming that man is born free and subject to no one, that society accordingly is a crowd of foolish men who stupidly yield to priests who deceive them and to kings who oppress them, so that the harmony of priest and ruler is only a monstrous conspiracy against the innate liberty of man.

Everyone must understand that such ravings and others like them, concealed in many deceitful disguises, cause greater ruin to public calm the longer their impious originators are unrestrained. They cause a serious loss of souls redeemed by Christ’s blood wherever their teaching spreads, like a cancer, it forces its way into public academies, into the houses of the great, into the palaces of kings, and even enters the sanctuary, shocking as it is to say so."

-Pope Pius VI, “Inscrutabile” (On The Problems Of The Pontificate)

Lactantius on the Free Will of Religious Association

"Oh with what an honorable inclination the wretched men go astray! For they are aware that there is nothing among men more excellent than religion, and that this ought to be defended with the whole of our power; but as they are deceived in the matter of religion itself, so also are they in the manner of its defense. For religion is to be defended, not by putting to death, but by dying; not by cruelty, but by patient endurance; not by guilt, but by good faith. … For if you wish to defend religion by bloodshed, and by tortures, and by guilt, it will no longer be defended, but will be polluted and profaned. For nothing is so much a matter of free will as religion; in which, if the mind of the worshiper is disinclined to it, religion is at once taken away, and ceases to exist."
Lactantius, “The Divine Institutes, in “Fathers of the Third and Fourth Centuries,” in The Ante-Nicene Fathers, 156-7.

Monsignor Ronald Knox's Test for Defining Christians

"The fideles, be they many or few, be their doctrine apparently traditional or apparently innovatory, be their champions honest or unscrupulous, are simply those who are in visible communion with the see of Rome… And in fact there can be little doubt that, in the West, our labeling of this party as orthodox and that as heterodox in early Church history comes down to us from authors who were applying this test of orthodoxy and no other."