So infallibility does not mean that there exists a man who in whatever he talks is infallible; since the decision 80 years ago, no pope did anything which is infallible, in the strict sense; but then he did something. And as I heard yesterday, when President Shuster of Hunter College (who is a Catholic) spoke at our faculty luncheon, he was (recently) the governor of Bavaria, the most Catholic part of Germany, and he was also in connection with Rhineland Catholicism. He said there was a very hopeful development of cooperation between Protestants and Catholics.

But in the moment in which this doctrine was proclaimed, cooperation almost ceased. Now he hopes that it will return again, but this showed to the Protestant and to the secular world – to all of us – that these dogmas about the infallibility of the Pope are taken absolutely seriously, without restriction. We should have known this always. Now we are reminded of it again. And this means there is no approach, from a Protestant or humanist point of view, to this doctrine and its implications.

This was finally confirmed in the fourth important point: The Pope is irreformable, by any action of the church. You must compare this with the impeachment procedures ,which in America is possible against any president; they are very rare, but they have happened and can happen again. They happened, of course, against the pope in the Middle Ages, and some popes were dispossessed, removed, and others put in their place. All this came to an end in 1870, because there is no power which can remove a pope. The pope is in this sense absolute and irremovable. No impeachment is possible. In this way, implicitly every dogma formulated by the pope is valid. This means that, for instance, one doctrine which was formulated before 1870 – the doctrine of the Immaculate Conception of Mary the Virgin, in the birth of Christ, which the Franciscans wanted to have all the time was now de fide, while before that the Dominicans, who were against it, still could say that it is not a valid dogma. Now it is a valid dogma because of the implication that the pope has accepted it ex cathedra.

There was a last strong movement in the Roman church back to the original Augustinianism of the church. This movement is called according to a man named Jansen, Jansenism. The Jesuit Molina wrote against the Thomistic Dominicans who teach, as you remember, the doctrine of predestination. The Jesuits were against this doctrine and they fought for human freedom. The doctrine of predestination, although it is a strong Augustinian doctrine, was revoked. But now Jansen and the Jansenists – he most important of them is Pascal – arose and fought against the Jesuits. But the Jesuits prevailed, The popes followed them. The Jesuit was the modern man, in the Roman church – disciplined; very similar to totalitarian forms of subjection as we experience them today; completely devoted to the power of the church; and at the same time nourished with much intellectual education and modern ideas, deciding for freedom and reason.
Paul Tillich, A History Of Christian Thought – Table of Contents