From past and present, here are some of the things that have been said about papal authority and infallibility:
UNLESS I am convinced by the testimonies of Scripture or evident reason (for I do not believe either Pope or councils alone, since it is certain that they have both erred frequently and contradicted themselves) ... I neither can nor wish to revoke anything.
Martin Luther at Worms (1521)
The dogma has been divinely revealed: that the Roman Pontiff, when he speaks ex cathedrathat is, when carrying out the duty of the pastor and teacher of all Christians in accord with his supreme apostolic authority...