Roman Catholicism is a sprawling, wildly diverse community of 1.2 billion people spread over every nook and cranny of the planet, and sometimes, when its fault lines and internal tensions seem especially sharp, it almost defies belief that the Church has held together as long as it has.

Theologically, of course, one would say that the agent of unity is the Holy Spirit. Sociologically and politically, however, there’s no question what keeps the Church from spinning apart: It’s the pope.

No other religious group with a global following has such a clear center of authority. (Try asking yourself sometime, for instance, who’s in charge of Islam, or Judaism, or Hinduism, and you’ll get the idea.)

One could almost say that to be Catholic – in a very loose, non-catechetical way of putting things – means to take the papacy seriously. That doesn’t imply agreeing with popes on all points, and certainly not believing that absolutely everything in Catholic life does or should pivot on the pope, but rather, at some pre-conscious, gut level, just to be fascinated by the whole thing.

Over twenty years of covering the Vatican, I’ve met all kinds of Catholics who exude that instinct.

I’ve dined with “Black Nobility” in Rome, who still believe popes should be ruling over central Italy as secular monarchs. I’ve met liberal theologians from Western Europe who’ve spent their careers making arguments as to why the papacy should be deconstructed — which is, of course, a backhanded tribute to the office.

I’ve met countless ordinary Catholics who weep, who become speechless and almost paralyzed, to be in the physical presence of a pope – even if that means being stuck in the back of a vast crowd, when they would have had a better view of the action staying home and watching it on TV.

For enthusiasm, commitment and sheer passion, however, I’ve never met anyone quite so passionate about popes as Fr. Richard Kunst of the Diocese of Duluth in Minnesota.

I was in Duluth this week to speak at the College of St. Scholastica, which afforded me the chance to reconnect with Kunst. Over the years, he’s put together one of the most remarkable collections of papal memorabilia you’ll ever see outside the Vatican museums.

You can find an overview of his collection on-line at http://www.papalartifacts.com, which is maintained by one of Kunst’s parishioners named Mary Sitek.

Kunst has got a little bit of everything. There’s an 1870 letter signed by Pope Pius IX, for instance, thanking Bishop Pierre de Dreux-Breze of Moulin for his support for dogma of papal infallibility at Vatican I, written the day before the dogma was pronounced.

Kunst has got all the lead seals that were used to block off portions of the Vatican during the 1978 conclave that elected Pope John Paul II, and he’s also got the vestments St. John Paul wore on his 1993 trip to Denver for World Youth Day.

He’s got papal coins and holy cards, Swiss Guard uniforms and heraldry, postage seals from the era of the Papal States, bricks from the holy door at St. Peter’s Basilica, and pretty much everything else one could imagine. Recently he came back from Rome having convinced Pope Francis to autograph a baseball.

Basically, if a pope signed it, touched it or wore it, Kunst probably has it. All in, he’s got several hundred items in the collection – thousands, actually, if you count papal coins.

Kunst’s story is that as a high school senior, he had an assignment in a government class to write a politician. He wrote U.S. President Jimmy Carter, who sent a signed photograph, and the collecting bug was planted. Kunst eventually had the signatures of 16 U.S. presidents, stretching back to Martin Van Buren.

In 1995, Kunst says, he saw a dealer catalog offering three papal signatures. He had to take out a loan from his sister, but he got two of them – from Popes John XXIII and Paul VI, both from their time as cardinals.

In parallel fashion, Kunst was moving toward the priesthood. Once ordained, he said, he had a steady income to devote to his collection, and it took off in earnest. He says that aside from his ministry as a priest – he’s currently pastor at St. John the Evangelist in Duluth – this is his life’s work, and he devotes 75 percent of his small salary to scouring the world for new additions.

After seeing him this week, I asked Kunst to put in one sentence why he does all this. In the classic fashion of a collector, however, he couldn’t resist adding an item, and gave me two.

“It gives a unique opportunity to have a tangible connection to the men who were the Vicars of Christ,” he said. “It is a collection for the purpose of fostering love for our Holy Fathers.”

Kunst says that someday he hopes a big-time Catholic college or university will provide a suitable museum-quality setting for the collection. I understand that desire, though part of me hopes it stays in Duluth and becomes a pilgrimage destination, because there would be something entirely apt about that happening in a place that’s by no means a crossroads of Catholic culture.

It would be a good lesson, in other words, in the universality of the Church.

Wherever it ends up, the take-away from all this is simple. What most Catholics have in limited doses, Father Richard Kunst has in spades … this unavoidable, ineradicable, spiritual DNA-level conviction that the papacy, whatever else one makes of it, just matters.