Is the Pope Catholic/Infallible?

Two commentators, neither of them Catholic, have demonstrated that although the Pope's Catholicity can hardly be called into question, his charism of infallibility is one of the most misunderstood doctrines of the Church.

Yusuf Islam, the artist once known as Cat Stevens (who apparently had a Catholic schooling), believes that the Regensburg affair has demonstrated that the Pope is not infallible.

Mike Hume of Spiked-Online also thinks the Regensburg affair reflects badly on the infallibility of the pope.

But hold on guys. We have never said that the Pope is an infallible interpreter of Islam or history, but rather of Catholic faith and morals. Nor have we ever said that the Pope is infallible when he speaks from his old professorial cathedra in Regensburg, but only when he speaks from the Cathedra of St Peter in Rome.

After all, the Pope is Catholic.