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Evan Horowitz | Quick Study

When is the pope considered infallible?

Pope Francis addressed a joint meeting of Congress.Jonathan Ernst/REUTERS

Popes claim to have a power that no one else possesses — not kings or queens, presidents, prime ministers, or CEOs. According to the Catholic Church, Pope Francis, like his many predecessors, has the ability to speak infallibly on certain subjects, without the possibility of error.

Rarely, though, do popes actually make use of this authority. In his two years as pope, Francis has never made a pronouncement that would qualify. In fact, only one papal statement of the past century is generally accepted as infallible by the church: Pope Pius XII’s affirmation of the Assumption of Mary in 1950.


So when Pope Francis addressed Congress Thursday, he wasn’t speaking as the infallible representative of the Catholic Church but rather as an extremely popular and globally respected religious leader.

When is the pope considered infallible?

For a papal statement to be treated as infallible, it has to meet strict criteria.

To begin with, the pope must be speaking “ex cathedra,” which means he has to be acting in his role as head of the church, “shepherd and teacher of all Christians.”

Also, the topic has to involve “faith or morals” — not whether Tom Brady deflated footballs — and must be binding for the church as a whole.

Only in these circumstances does the Catholic Church consider the pope’s words infallible. And such circumstances don’t arise often. Pius XII’s statement about the assumption of Mary is the only agreed-upon infallible claim of the last 150 years.

Having said that, it’s not always clear whether the criteria for infallibility have been met, or not, which leaves room for argument about which statements count as infallible. The church doesn’t keep a complete or definitive list.

Among the potentially infallible statements is the 1994 letter of Pope John Paul II reaffirming the church position that only men can become ordained priests. Some church leaders consider it infallible, but not all scholars agree.


Have popes always been thought infallible?

This question is trickier than it sounds. The doctrine of papal infallibility was officially promulgated by the Catholic Church in 1870, as part of the first Vatican council.

But the council wasn’t suggesting that popes would be able to speak infallibly from them on. It was saying, instead, that popes had always been able to speak infallibly, even before the idea was codified by the church.

Many of the well-accepted, infallible papal pronouncements come from popes in power before 1870. For instance, Pope Leo I’s writings on the two natures of Christ (divine and human), from around 450 AD.

What about popes who were wrong?

When Republican presidential candidate and practicing Catholic Chris Christie said the other day that he thought Pope Francis was wrong to urge stronger diplomatic ties between the US and Cuba, Christie wasn’t defying the church, or questioning the legitimacy of papal infallibility. He was saying something that the church readily accepts: Sometimes, popes are wrong.

They make errors both ordinary and extraordinary. One seventh-century pope was kicked out of the church (after his death) for having taught a heresy. Several popes were involved in the misguided effort to defend an earth-centered view of the universe against the revolutionary findings of Galileo.

But so long as these mistakes are made in situations that don’t fit the criteria for infallibility, there’s really no problem. Errors arise in situations when errors can arise. Or, as Pope John XXIII cleverly put it: “I am only infallible if I speak infallibly but I shall never do that, so I am not infallible.”


Are popes the only church figures considered infallible?

No. Bishops can speak infallibly when acting together, as when they meet in an ecumenical council.

Broadly speaking, it’s really the church that claims infallibility. Popes and bishops are the agents for expressing that infallibility.

What does this mean for Pope Francis’ visit?

When Francis addresses Congress, and speaks to crowds in New York and Philadelphia, he speaks with the authority and long-accumulated wisdom of the Catholic Church.

But he has never yet invoked his church-endorsed power to speak infallibly, and there’s no reason to think he’s planning to start this week.

Evan Horowitz digs through data to find information that illuminates the policy issues facing Massachusetts and the United States. He can be reached at evan.horowitz@globe.com. Follow him on Twitter @GlobeHorowitz