RIO DE JANEIRO, Dec 26 — Neighbours from surrounding apartment buildings toss empty beer bottles through a gaping hole in the roof of the once-majestic church. Pigeons roam the cavernous nave, their excrement piling up on the floor. A watchman guards treasures from the thieves who prey on the city’s derelict buildings.

The neoclassical Positivist Church of Brazil, with its soaring columns and a cryptic sign above its entrance proclaiming, "The Living Are Forever and Increasingly Governed by the Dead,” was long a captivating sight on Benjamin Constant Street near the old city centre.

These days, the crumbling, graffiti-tagged church, whose freethinking founders helped modern Brazil rise from the ashes of an empire, is just another emblem of how Rio de Janeiro neglects its past, allowing grandeur to fall into ruin.

"Congregants once gathered here to debate incendiary ideas originating in Paris, the holy city for the positivists,” said Christiane Souza, 48, the church’s heritage director. "Tragically, our institution now finds itself in a state of neglect, as if history is something Brazil should disdain.”

The bust of Auguste Comte, left, the French founder of positivism, sits among other busts in the basement of the Positivist Church of Brazil in Rio de Janeiro, December 22, 2016.

Indeed, few Brazilians know much about positivism, the secular religion that was spread in Brazil in the second half of the 19th century by followers of French philosopher Auguste Comte, except, perhaps, that two of his tenets — order and progress — remain emblazoned on the Brazilian flag.

Roughly defined, Comte’s philosophy of positivism sought to reorganise society around the concept that explanations derived from science should be prized as a way of understanding the world. Positivism drew admirers in places including Mexico, Britain and Turkey. Taking things a step further, Comte created his own religion to spread his beliefs.

Some facets of his Religion of Humanity resembled Roman Catholicism. The interior of the decaying church in Rio still has the feel of an austere cathedral, albeit one where services stopped after part of the roof collapsed during a storm in 2009. Worshippers exalted a female icon similar to the Virgin Mary and modelled on Clotilde de Vaux, with whom Comte was in love.

A depiction of Clotilde de Vaux, a woman whom Auguste Comte, the father of positivism, was in love with, in the Positivist Church of Brazil in Rio de Janeiro, December 22, 2016.

But Comte also told followers to worship humanity, not God, and created a new calendar. Its starting year was 1789, when a mob stormed the Bastille in a defining moment of the French Revolution; he named months after historical titans like Gutenberg, Charlemagne, Shakespeare and Dante.

Brazil, a slaveholding empire ruled by a monarchy for most of the 19th century, was fertile ground for the Religion of Humanity. Francophile adherents to the faith included leading figures in the tumultuous period after the 1889 coup that toppled Brazil’s emperor, such as Cândido Rondon, the explorer who mapped out far-flung stretches of the Amazon rain forest with Theodore Roosevelt.

In other countries, the site where such luminaries assembled might today be enshrined as a museum. Not in Rio, where authorities last year opened a lavish Museum of Tomorrow to contemplate the future, even as Belle Époque buildings in the city waste away in various stages of decay.

Century-old pamphlets written by positivists in French and Portuguese, in the Positivist Church of Brazil, in Rio de Janeiro, December 22, 2016.

Still, Giovanni Fernandes, custodian of the Positivist Church, sometimes lets a visitor or two slip inside, offering a glimpse into Brazil’s not-so-distant past. Scattered around the entrance are century-old pamphlets in Portuguese and French that the positivists once printed in the basement.

The titles of the rotting booklets reflect the issues, political infighting and prejudices that used to consume Brazil: "Obligatory Vaccination and the Politics of the Republic,” "The Question of the Border Between Brazil and Argentina,” "In Defence of Brazilian Savages.”

One room with a spiral staircase contains a trove of sculptures shrouded in dust, including a statue of Clotilde de Vaux cradling an infant. Decaying paintings on the wall seem to depict aristocrats in European-style attire lost in philosophical reflection.

Once in a while, scholars emerge from the church with coveted discoveries, as when a mildewy drawer stuffed with old papers yielded the original sketches for Brazil’s flag, which positivists created over the objections of rivals who wanted one modeled on that of the United States.

"There’s so much dust and grime in here that occasionally I tell visitors they should bring a surgical mask,” said Fernandes, 57, the church’s lonely watchman. "I’m often asked if the building is haunted, and I reply, ‘No, I wouldn’t work alongside any ghosts.’”

Until around a decade ago, a dwindling group of about 10 congregants still convened in the church for services, before the roof collapsed. Now the descendants of devotees donate their own time and meagre funds to keep the building from collapsing altogether.

"We have thousands of rare books in here, not to mention statues, paintings, banners, ledgers, correspondence and who knows what else,” said Souza, the heritage director, whose father, Danton Voltaire Pereira de Souza, led the church until his death in 2014.

"It saddens me to think we may be among the last of the positivists,” she said, leaning on scaffolding that was part of an abandoned restoration effort. "Sometimes it feels like we are standing against oblivion.” — The New York Times