If anyone says that not only the increase of faith but also its beginning and the very desire for faith, by which we believe in Him who justifies the ungodly and comes to the regeneration of holy baptism -- if anyone says that this belongs to us by nature and not by a gift of grace, that is, by the inspiration of the Holy Spirit amending our will and turning it from unbelief to faith and from godlessness to godliness, it is proof that he is opposed to the teaching of the Apostles, for blessed Paul says, "And I am sure that he who began a good work in you will bring it to completion at the day of Jesus Christ" (Phil. 1:6). And again, "For by grace you have been saved through faith; and this is not your own doing, it is the gift of God" (Eph. 2:8). For those who state that the faith by which we believe in God is natural make all who are separated from the Church of Christ by definition in some measure believers.
FR Catholics; what do YOU say to THIS?
Therefore, if anyone says that it is not by the institution of Christ the lord himself (that is to say, by divine law) that blessed Peter should have perpetual successors in the primacy over the whole Church;
or that the Roman Pontiff is not the successor of blessed Peter in this primacy: let him be anathema.
--Vatican 1, Ses. 4, Cp. 1