Papal Infallibility
In order to refute the Catholic doctrine of the infallibility of the Pope on matters of faith and morals (no, the Pope is not infallible on something like economics), it is quite sufficient to locate a single ex cathedra pronouncement that was later declared invalid, revised, or is clearly false. This should be easy enough, given the 2,000 years of Church history. My question is, has any such been produced?
It follows, by the way, that our doctrine is at the very least highly falsifiable, a virtue even if some say it has no others.