The theme of this year’s Metropolitan Museum Costume Institute exhibit — “Heavenly Bodies: Fashion and the Catholic Imagination” — is bound to cause controversy. Showing priestly vestments and risqué haute couture alike, the exhibit seems primed to cause tension between the secular and the sacred.

But there’s another, quieter controversy brewing over Catholicism and fashion — not between the sacred and the profane but between different interpretations of the sacred. The elaborate 19th-century priestly vestments that will be part of the current exhibit, dating back to a time of particular pomp in the Catholic Church, evoke a debate that is going on in the church right now.

The question of what priests and popes should wear — and the scale of grandeur they should evoke — ties into a much wider ecclesiastical culture clash over liturgy, pomp, and tradition.

That debate, according to David Gibson, director of Fordham University’s Center of Religion and Culture, dates back all the way to the Reformation but has been particularly pronounced within Catholicism over the past 50 or so years.

Priestly clothes, Gibson says, are “wrapped up in everything.” Debates over how priests and popes should dress are also, he says, about liturgy, about tradition, and about papal power.

Papal dress ties into a bigger question about Catholic tradition

Papal vestments, Gibson pointed out, are a lightning rod for questions about the church’s response to modernity more generally.

While there have always been Catholic orders that dressed simply — monastic orders like the Franciscans and Dominicans, for example — throughout most of church history the priests who participated at Mass by and large tended to wear ornate (and expensive) vestments. Watered silks and other weighty, pricey fabrics were customary, and in the higher echelons of the Vatican hierarchy, so was jewelry.

The latest round of questions over the appropriateness of priestly pageantry dates back to 1962-5 Second Vatican Council (more commonly known as Vatican II), a summit at which the church contended, in a variety of ways, with how to engage more meaningfully with a rapidly changing, secularizing world. Some of these changes, for example, involved transitioning from a Latin Mass into Mass said in local languages, or having the priest face worshippers instead of the altar. In that vein, since Vatican II, papal and priestly dress has tended to the more austere: a rejection of what was seen, by many, to be outdated and out-of-touch pomp and circumstance.

As one anonymous priest quoted by the Guardian put it, “The Church processed into the second Vatican council in cloth of gold and watered silk, and shambled out of the other end in drip-dry horse blankets and polyester.”

Since then, papal clothing has been one canvas by which debates over Vatican II played out.

So, for example, during his papacy from 2005 to 2013, the conservative Benedict XVI embraced some of the more “old-school” papal looks. He made headlines for wearing particularly extravagant items, like the ermine-trimmed mozzetta cape and the red, Santa-hat-like camauro, which had fallen into disuse after Vatican II.

At one point, the Vatican had to issue a stern statement informing worshippers, “The Pope is not dressed by Prada, but Christ,” after the media began to speculate about a particularly striking pair of red slippers he was fond of wearing.

For critics and admirers alike, Benedict’s clothing was visual shorthand for his policies: He was a traditionalist, wary of certain “modernizing” elements of Vatican II.

By contrast, consider Pope Francis. His notably simple clothing choices and rejection of more magnificent vestments also sound a refrain of his papacy: concern with the poor, and a distrust of the trappings of wealth more generally. During his first balcony visit as pope, for example, he did not wear the mozzetta Benedict XVI had brought back in style. (Apocryphal accounts also have him saying “the carnival is over,” referring to Benedict XVI’s fondness for striking clothing, although the veracity of this is debatable.)

Meanwhile, many of Francis’s major traditionalist critics — most notably his outspoken opponent American Cardinal Raymond Burke — often choose particularly bombastic clothing styles, in part as a nod to the traditionalism they would like to see the pope embrace.

Doing a breakdown of just one of Burke’s outfits — which included a gold mitre, a gold chasuble (tunic), a heavy gold pectoral cross necklace, a gold crozier (a staff that resembles a shepherd’s crook), and more — the Global Post estimated it cost about 15,000 British pounds (or a little over $20,000).

“You’ve got a resurgent revival of Catholic nostalgia, for old traditions,” says Gibson, noting that “this isn’t just nostalgia.” Rather, he says, “This is all of a piece, this Catholic traditionalism, with the theology of the church and its doctrine.” It’s not just about wanting to return to the aesthetics of an older church, he says, but about returning to its politics as well.

When, for example, “you see Cardinal Burke swishing around in yards of watered silk ... it signifies a return to the old days ... and also the old ways.”

To reduce the debate over Catholic aestheticism to “old versus new,” of course, would be too reductive. Among young Catholics, there is a revivalist strain of modern traditionalism. It can be found the depths of the internet phenomenon Weird Catholic Twitter, which is exactly what it sounds like, as well as in the aesthetic extravagance embraced by the fictional Pope Lenny (a.k.a. Pius XIII) of Young Pope: a staunch traditionalist whose youth only accentuates the vigor with which he defends Catholicism’s old ways. And, in some cities in American and all around the world, attendance at the pre-Vatican II form of the Mass (the Latin, or Tridentine, Mass) is on the rise. “It’s trendy to be a traditionalist in the Catholic Church,” concluded the Economist.

Visual beauty has always been a vital part of Catholic spirituality

At times, the media has treated Catholic aesthetic excess as something to mock, or to treat as vaguely campy fun (see: Benedict XVI making various “best-dressed” lists).

But, Gibson notes, the beauty of the priestly vestments, like the beauty of Catholic churches more generally, has always been a major part of Catholic spirituality. The liturgy — the ritual by which Mass is celebrated and the Eucharist (communion) taken — is, Gibson says, quoting the Catholic catechism, “the summit and source of the Catholic celebration.”

After all, in Catholicism (unlike in Protestant denominations), the Eucharist is taken literally: The wafer and wine become the body and blood of Jesus Christ. The act of Eucharistic celebration, in Catholic terms, is thus all the more mystical, something that Gibson characterizes as demanding an aesthetic commensurate to the sheer emotional and spiritual intensity of the act.

“It’s about beauty. Look at the cathedrals Catholics built over the ages. Look at the art — we love it! You look at that in awe. That’s a reflection of Catholic belief and the Catholic imagination,” he says.

Priestly vestments, Gibson argues, are part of the Catholic tradition of celebrating beauty. “It doesn’t make a lot of sense for the celebrant to be dressed in sackcloth and ashes,” he says. “The vestments are supposed to part of this beautiful liturgical tradition.”

When you see vestments in the context of the churches they were initially supposed to be worn in, Gibson says, “it all suddenly makes sense.” Vestments might look over-the-top in a vitrine at the Met, but within the context of the great historic churches of Rome, they fit right in.

The Catholic visual tradition is in part a function of necessity

But the sheer scale of so much of historic Catholic visual culture — altars, frescoes, and vestments alike — is as much due to necessity as theology.

For centuries, after all, spectacle was an integral part of Catholic culture, in part because the people attending Mass wouldn’t necessarily have access to other forms of information. Your average European peasant wasn’t literate (plus, Bibles translated into vernacular languages like French, German, or English were rare until the 16th century). The pomp and circumstance of the liturgy — from stained-glass windows to priestly vestments — was, in part, a means of conveying theological information visually to a population that wouldn’t necessarily have other ways to get it.

In contrast, consider the visual culture of Protestantism — traditionally, though not exclusively, less aesthetically bold than that of Catholicism. The Protestant aesthetic is defined, in part, by the fact that Protestantism developed among people who no longer needed that visual shorthand. After all, it was the 16th-century proliferation of the printing press that made Martin Luther so able to disseminate his writings (often among a bourgeois and literate class). The classically Protestant focus on text as opposed to liturgy can be attributed as much to technology as to theology.

Historically speaking, the Protestant Reformation bore out these tensions between visual and textual cultures. On the one hand, as Gibson notes, you had the “smashing of the icons, the stripping of the altars”: Protestant attempts to counter the Catholic Church’s excesses. On the other hand, you had the Catholic Counter-Reformation, in which Catholics seeking to reestablish their religious influence did so by the creation of some of the most magnificent baroque churches in history, painted by artists like Tintoretto and Titian. “That was a culture war, in a very literal way, just as it was a war of religion,” Gibson says.

Even today, Catholicism has maintained a visual focus in a way most Protestant traditions have not. But in an era when your Catholic worshippers are presumed to be largely literate, and capable of accessing theological ideas verbally as well as visually, that focus is no longer as imperative as it once was.

Plenty of Francis’s critics have wondered if he is the “first Protestant pope.” When it comes to his dress sense, at least, they may be right.

It’s unclear the extent to which the Met exhibit will feature quieter, less showy ecclesiastical robes as well as, well, “Catholic bling.” Many of the featured images on the Met website depict particularly ornate 19th-century garments — indicative of a particularly reactionary time in Catholic history. But the contrast between the featured items on display and Pope Francis’s wardrobe is striking.

In this, at least, Francis has succeeded in changing the church.