Not until 18th July, 1870 were Catholics assured that the Pope is infallible The decree reads as follows: " That the Roman Pontiff, when he speaks ex cathedra (that is, when—fulfilling the office of Pastor and Teacher of all Christians -... he defines a doctrine concerning faith or morals to be held by the Universal Church) through the divine assistance promised him in blessed Peter, is endowed with that infallibility, with which the Divine Redeemer has willed that His Church... should be equipped."
First, notice how cleverly the decree is worded to define infallibility and at the same time leave room for Popes to be mistaken, to be evil livers, and even for three rival Popes to curse each other. It cannot be denied that these things have happened.
Note, in the second place, that the Scriptures quoted to prove that infallibility was promised to " blessed Peter " have nothing at all to say about infallibility. " To the infallibility of St. Peter and his successors the following texts of Holy Scripture bear testimony: First from St. Luke (22: 32), where we read that our Savior addressed St. Peter in the presence of the other Apostles thus: "'Simon, Simon, behold Satan hath desired to have you, that he may sift you as wheat. But I have prayed for THEE that THY faith fail not: and THOU being once converted, confirm thy brethren!'" (Catholic Belief, p. 39).
We do not suppose that Catholics, who do not generally read their Bibles, will see how grotesquely inappropriate such a Scripture is in this connection. Peter was about to have a very grievous fall, to deny his Lord with oaths and cursing. The Lord, who foresaw this, told him of His high-priestly prayers for him, that he might not sink under the sorrow of his shame, but be restored, and become useful again to his brethren. There is not a word about infallibility, or the power of handing this on to his successors.
Another Scripture quoted is Matthew 16:1818And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it. (Matthew 16:18), which we have already seen does not refer to Peter as the rock on which the Church was to be built, but to our Lord Himself. Another Scripture is quoted: "A third argument is drawn from these words of Jesus Christ addressed to St. Peter: 'Feed My Iambs... feed My lambs... feed My sheep'" (St. John 21:15-1715So when they had dined, Jesus saith to Simon Peter, Simon, son of Jonas, lovest thou me more than these? He saith unto him, Yea, Lord; thou knowest that I love thee. He saith unto him, Feed my lambs. 16He saith to him again the second time, Simon, son of Jonas, lovest thou me? He saith unto him, Yea, Lord; thou knowest that I love thee. He saith unto him, Feed my sheep. 17He saith unto him the third time, Simon, son of Jonas, lovest thou me? Peter was grieved because he said unto him the third time, Lovest thou me? And he said unto him, Lord, thou knowest all things; thou knowest that I love thee. Jesus saith unto him, Feed my sheep. (John 21:15‑17)).
In these simple words addressed to Peter there is nothing about infallibility, or the power to hand it on to successors in the papal chair. As an argument, it is quite beside the mark. Keen minds in the Church of Rome must be aware that all these pretensions are quite foreign to Scripture.