The papacy for dummies

The first condition of salvation is to keep the norm of the true faith and in no way to deviate from the established doctrine of the Fathers. For it is impossible that the words of our Lord Jesus Christ, who said, "Thou art Peter, and upon this rock I will build my Church," [Matthew 16:18], should not be verified. And their truth has been proved by the course of history, for in the Apostolic See