Pope Pius IX
And here, beloved Sons and Venerable Brothers, We should mention again and censure and very grave error in which some Catholics are unhappily engaged, who believe that men living in error, and separated from the true faith and from Catholic unity, can attain eternal life. Indeed, this is certainly quite contrary to Catholic teaching. It is known to Us and to you that they who labor in invincible ignorance of our most holy religion and who, zealously keeping the natural law and its precepts engraved in the hearts of all by God, and being ready to obey God, live an honest and upright life, can by the operating power of divine light and grace, attain eternal life, since God who clearly beholds, searches, and knows the minds, souls, thoughts, and habits of all men, because of His great goodness and mercy, will by no means suffer anyone to be punished with eternal torment who has not the guilt of deliberate sin.
But, the Catholic dogma that no one can be saved outside the Catholic Church is well-known; and also that those who are obstinate toward the authority and definitions of the same Church, and who, persistently separate themselves from the unity of the Church, and from the Roman Pontiff, the successor of PETER, to whom “the guardianship of the vine has been entrusted by the Savior,” cannot obtain eternal salvation.
But, God forbid that the sons of the Catholic Church ever in any way be hostile to those who are not joined with us in the same bonds of faith and love; but rather they should always be zealous to seek them out and aid them, whether poor, or sick, or afflicted with any other burdens, with all the offices of Christian charity; and they should especially endeavor to snatch them from the darkness of error in which they unhappily lie, and lead them back to Catholic truth and to the most loving Mother the Church, who never ceases to stretch out her maternal hands lovingly to them, and to call them back to her bosom so that, established and firm in faith, hope, and charity, and “being fruitful in every good work” (Col. 1:10), they may attain eternal salvation.
From the encyclical, Quanto conficiamur moerore, to the bishops of Italy, Aug. 10, 1863