ROME – Papacies, almost by definition, are complex affairs. Popes govern the world’s largest and most complicated religious institution, and they do it for a relatively long span of time. Over the arc of the last ten, the average length has been 14.5 years, which is roughly three and a half U.S. presidential terms – longer than FDR, for instance, led America through the New Deal and World War II.

Over such a span, popes do a staggering number of things. They publish encyclical letters, they issue decrees, they erect and suppress dioceses and orders, they appoint bishops and Vatican officials, they engage political questions, they sign treaties, they encourage some movements in Catholic life and put down others, they fight some scandals and arguably cause others, and, more recently, they’ve also taken important international trips.

Given such a flurry of activity, any effort to reduce a papal legacy to a quick sound-bite inevitably will be over-simplified, reductionistic, misleading, and, quite possibly, a total waste of time.

That said, let’s do it anyway!

Thinking about the ten completed papacies since the election of Leo XIII in 1878 – the first after the collapse of the Papal States, and thus marking the birth of the modern papacy – I’ve come to believe that at the popular level, the most memorable legacy of a pope usually can be expressed in a simple, two-word formula.

To be clear, this is not about identifying the best or worst thing a given pope did, or the most important, or the holiest, or anything else. The idea is simply to peg what regular people with a general interest in church affairs, as opposed to specialists and academics, likely recall about a given papacy over the course of time.

So, let’s take my two-word theory out for a spin and see what it can do. We’ll leave Francis out of consideration for now, since his papacy is still a work in progress.

  1. Leo XIII (1878-1903): Social Teaching

Almost 125 years after Leo’s death, what most ordinary Catholics likely can remember, maybe from a course in school or from hearing it a homily somewhere along the line, is that Leo XIII launched the modern tradition of Catholic social teaching, and especially the church’s analysis of economic justice. He did so with his 1891 encyclical Rerum Novarum, which tackled the situation of the working classes in the new capitalist order being born.

  1. Pius X (1903-1914): Anti-Modernism

Okay, I conceded that “anti-modernism” actually is one word, not two, but it contains two ideas: Modernism, and being against it. That’s likely what most people today could summon to mind about Pius X’s reign: Loyalty oaths, condemnations, spying networks in the guise of sodalities, and other strenuous efforts to combat the rise of “modernism” – broadly meaning détente with science, secularism and contemporary philosophy – in Catholic theology.

  1. Benedict XV (1914-1922): “Useless Slaughter”

Benedict’s reign was defined by the First World War and its aftermath, and what most remember today was the pope’s valiant but futile efforts to end the conflict, famously captured in his description of it as an inutile strage, or “useless slaughter.” His diplomatic and moral efforts failed at the time, but later his warnings about mounting European nationalist resentments after the war were seen as prophetic.

  1. Pius XI (1922-1939): Lateran Pacts

With the agreements between Italy, governed at the time by fascist Prime Minister Benito Mussolini, and the Vatican under Pius XI, the famous “Roman question” was definitively settled, marking the end of the papacy’s political isolation and, more broadly, its acceptance of modern secular states and church/state separation. It also, of course, filled the Vatican’s coffers with compensation for its lost territories, providing a financial patrimony for its operations to this day.

  1. Pius XII (1939 – 1958): Holocaust “Silence”

However unjust it may be, what most people likely could tell you today about Pius XII’s 18-year reign – arguably the most fraught and anguished of any on this list – is that there’s a debate about whether he did enough to denounce the Holocaust and to save Jews and other victims of the Nazis. The case for the prosecution was most famously expressed in John Cornwall’s polemical 1999 book Hitler’s Pope.

  1. John XXIII (1958-1963): Vatican II

This one’s a no-brainer. By far, what history will recall about “Good Pope John” is his surprise decision to summon the Second Vatican Council (1962-65), and all the earthquakes in Catholic life it triggered. He didn’t live to see the council’s end, but his vision in calling it and opening it, including his celebrated “prophets of doom” speech, were decisive for everything that followed.

  1. Paul VI (1963-1978): Humanae Vitae

Another slam-dunk here, as Paul VI’s landmark 1968 encyclical letter reaffirming the church’s traditional ban on birth control remains by far the most discussed, and debated, aspect of his papacy. To this day, Humanae Vitae is probably one of only a handful of papal encyclicals that even non-Catholics would not only recognize, but they’d have an opinion about it.

  1. John Paul I (August-September 1978): Smiling Pope

Though he reigned for only 33 days, Pope John Paul I nevertheless managed to leave a legacy simply by representing a breath of fresh air. After the perceived gloom and doom of the late Paul VI years, this charming, engaging figures seemed to invest the papacy with a new lease on life, quickly earning the moniker of a “smiling pope” that follows him to this day.

  1. John Paul II (1978-2005): Ended Communism

This is toughest call in the set, because John Paul II was around so long, shattered precedents on so many fronts, and left his mark on history in so many different ways, it’s obviously artificial to pick just one idea. Still, if you were to ask most ordinary folks, the first thing that likely would come to mind for most is the way his sponsorship of the Solidarity movement helped set the dominoes in motion that led to the collapse of the Berlin Wall and the end of the Soviet empire. Certainly, his fellow Poles do everything in their power to make sure no one ever forgets.

  1. Benedict XVI (2005-2013): He Quit

We end with another fairly easy choice. Though Benedict presided over a dramatic, and often turbulent, papacy, nothing he did will pass into history like the way it ended: With the first resignation in 500 years, and arguably the first ever under uncontested circumstances. In effect, Benedict became the Catholic Cincinnatus, a leader who had absolute power and voluntarily relinquished it when he believed his task was complete, becoming an eternal symbol of civic virtue.

There you have it: The popular legacies of ten popes, summed up in twenty words. I’m not sure if it qualifies as wit, but at least it has the virtue of brevity.