What Papal Infallibility Is (and Isn’t)

The words of God we have received are infallible, whether they come in written or unwritten form. In written form, they come to us in Scripture. In unwritten form, through Tradition. The Magisterium determines what is truly the word of God and what is merely of men.

The pope teaches that infallibility is what is contained in divine revelation. That simply means the Holy Spirit protects him from teaching error.

Many Catholics know this, but are not sure when the pope actually speaks infallibly. They hear Pope Francis say ambiguous things that seem to contradict prior Church teaching. They wonder how his off-the-cuff remarks relate to his supposed infallibility.

Here is a quick explanation of what infallibility is and isn’t.

The pope is only infallible when speaking on matters of faith and morals.
Christ made the pope the head of the Church, not of the World Health Organization or NASA. His task is to teach faith and morals, not health, science, or any other secular field (although he can speak on the doctrinal or moral implications of findings in secular fields).

Therefore, when you hear of past popes advocating for geocentrism or any other scientific idea, these do not undermine their infallibility. God does not protect them from error in all branches of knowledge.

The pope is not always infallible, even when speaking on faith and morals.
To speak infallibly, the pope must talk with the fullness of his authority and to the whole Church and make it clear that he’s pronouncing a definite teaching. (The phrase “I declare and define” in a papal document is usually a good sign of an infallible teaching.) He’s not infallible when speaking as a private theologian or as the bishop of the Diocese of Rome.

He’s also not infallible when teaching on faith and morals in a non-definite way. In this case, he may teach authoritatively, but not infallibly. You can read more about that difference here.

The Code of Canon Law has a good rule of thumb for identifying infallible teachings: “No doctrine is understood as defined infallibly unless this is manifestly evident.”

Infallibility doesn’t mean the pope will express things in the best way.
Infallibility means the Holy Spirit protects the pope from teaching error under the conditions listed above. It doesn’t mean the pope will state the teaching in the clearest way or offer it at the most opportune time.

Infallibility has nothing to do with the pope’s personal behavior.
Many Protestants — and even some Catholics — confuse infallibility and impeccability. Impeccability is the impossibility of sinning. That’s different from not teaching errors. Even if a pope is the greatest sinner of all, the Holy Spirit can still protect him from teaching the wrong doctrines.

Hopefully, this helps clear things up. Don’t be disturbed every time you hear a head-scratching statement from a pope. Popes rarely invoke their charism of infallibility, so all of the “contradictions” in papal teachings (which are not always contradictions if you study them closely) do nothing to undermine the credibility of the papal office established by Christ.