By DAVID GIBSON, Religion News Service     6/16/2015

The ‘Splainer (as in “You’ve got some ‘splaining to do”) is an occasional feature in which RNS staff give you everything you need to know about current events to hold your own at a cocktail party.

(RNS) When Al Smith ran for president in 1928, his status as the first Catholic to head a major party ticket was challenged by one writer on the basis that he would have to follow papal encyclicals, not the U.S. Constitution.

“What the hell is an encyclical?” Smith reportedly replied when the article in question was brought to his attention.

A friendly priest helped Smith craft a more detailed response (and Herbert Hoover won the race), but the term is still likely to elicit quizzical expressions even from diligent Catholics — and that’s in spite of the enormous prepublication buzz surrounding Pope Francis’ new encyclical on the environment.

Francis’ encyclical will be officially released on Thursday (June 18), so, to answer Smith’s question once again, here’s what you need to know:

Q: Okay, what is an encyclical?

A: An encyclical, as its name implies, is a “circular letter” meant to be spread throughout a community. A papal encyclical is a letter from a pope that can be addressed to the bishops and priests of a country or region, or the clergy of the entire world. Encyclicals can also be addressed to the entire Catholic faithful or — as Pope John XXIII did for the first time in his 1963 encyclical “Pacem in Terris” (“Peace on Earth”) — to all people “of good will.”

Q: What is an encyclical about?

A: A papal encyclical deals with some aspect of Catholic teaching — clarifying, amplifying, condemning or promoting one or a number of issues. It can focus on an aspect of Catholic faith or teaching, like birth control. Since Pope Leo XIII issued an encyclical on labor and social justice in 1897, popes have increasingly published encyclicals on issues of general concern, like peace or human rights.

Q: What is Francis’ encyclical about?

A: This encyclical from Francis is titled “Laudato Si’,” or “Be Praised,” from the famous “Canticle of the Sun” that St. Francis of Assisi wrote in medieval Italian around the year 1224. The hymn praises God and his creations, and speaks of “Brother Sun” and “Sister Moon,” and “our sister, Mother Earth, who sustains and governs us, and who produces various fruits with colored flowers and herbs.” It is the first papal encyclical ever devoted to the environment, and on a topic of growing concern, which is one reason it has attracted so much notice.

Q: Is this Francis’ first encyclical?

A: Technically, no. Francis published an encyclical called “Lumen Fidei” (“The Light of Faith”), a discourse on faith, on June 29, 2013, just three months after he was elected. But he was mainly finishing a draft that had been started by his predecessor, Benedict XVI, who left it unfinished when he retired. (Francis called it “the work of four hands.”) “Laudato Si’: On the Care of the Common Home,” is the first encyclical that is wholly Francis’ own idea and work.

Q: How many encyclicals have popes written?

A: While popes since the early centuries of the church issued periodic letters, the first letter called an encyclical was issued by Pope Benedict XIV on December 3, 1740. Since then, popes have written nearly 300 encyclicals. Pope Leo XIII (1878-1903) was by far the most prolific encyclical writer, penning 90 all together. St. John Paul II, by contrast, wrote 14 encyclicals, and Benedict XVI wrote three and left one unfinished.

Q: Are the pope’s pronouncements in an encyclical infallible?

A: The short answer is “No.” The longer answer is “It’s complicated.” Certainly, an encyclical is one of the most authoritative statements a pope can issue on his own. As theologian Richard Gaillardetz has explained, the positions in an encyclical do not, however, entail declaration of dogma or defined doctrine. They are rather matters of prudential judgment that believers and others should approach with an informed conscience.

That leaves a lot of room for debate, and given the contentious nature of the climate change debate, it’s likely that opponents of climate change and of Pope Francis are going to deploy the “prudential judgment” loophole early and often.

But many theologians caution that if they do, they do not properly understand encyclicals, papal authority, or the science on climate change.