Quote by Pope Gregory XVI

“14. We now come to another and most fruitful cause of the evils which at present afflict the Church, and which We so bitterly deplore; We mean indifferentism, or that fatal opinion everywhere diffused by the craft of the wicked, that men can by the profession of any faith obtain the eternal salvation of souls, provided their life conforms to justice and probity. But in a question so clear and evident it will undoubtedly be easy for Us to pluck up from amid the people confided to your care so pernicious an error. The apostle warns us of it: "One God, one faith, one baptism." Let them tremble then who imagine that every creed leads by an easy path to the part of felicity; and reflect seriously on the testimony of our Saviour Himself, that those are against Christ who are not with Christ, and that they miserably scatter by the fact that they gather not with Him, and that consequently they will perish eternally without any doubt if they do not hold to the Catholic Faith, and preserve it entire and without alternations. Let them hear Saint Jerome himself, relating that, at the epoch when the Church was divided into three parties, he, faithful to what had been decided, incessantly repeated to all who endeavored to win him over: "Whoso is united to the chair of Peter is with me." In vain did they attempt to create an illusion by saying that he himself was regenerated in water; for Saint Augustine answers precisely: "The branch lopped off has the shape of the vine; but what avails the form if it have not the root?”

Quote by Pope Gregory XVI