Christ turned to his disciples and said, “Other sheep I have, which are not of this fold: them also I must bring, and they shall hear my voice; and there shall be one fold, and one shepherd.”

Click to read photo caption. Photo by Mark Derewicz. ©2010 Endeavors magazine.

For centuries, Christians have used this passage from the Gospel of John as motivation to spread the word of Christ. But historian Brett Whalen found that medieval theologians also used it to foment a movement they hoped would spur on the End Times, an era of peace after Christ’s defeat of the Antichrist, when all peoples would accept Jesus or face the wrath of God.

But a funny thing happened on the way to the apocalypse. Several medieval popes and thinkers did usher in a sort of end time. Just not the one they had envisioned.

Whalen has a fascination with the Middle Ages. To him they weren’t that dark — only a bit gloomy. A pall was cast over Christian Europe in the eleventh century, Whalen says, when the one fold of believers turned into two: the Latin Church in Rome and the Eastern Church in Constantinople.

Whalen was researching the schism when he found that theologians seemed very concerned with the apocalypse. They said that Rome must reunite with Constantinople, and that Christians must become one community of believers before Christ would return. Some of these apocalyptic thinkers had the ear of the pope. But some were average clergymen, simply giving voice to thoughts commonly held during the High Middle Ages.

While researching rare documents at the Bibliothèque Nationale in Paris, Whalen noticed an early-eleventh-century manuscript titled Letter from A Humble priest to the Rulers of the Saracens (that is, Muslims). As far as Whalen could tell, it had never been published or even referenced by another researcher. “Everything in it was apocalyptic, trying to make sense of how God could allow Muslims to control the Holy Land,” Whalen says. The anonymous author wrote that God must have allowed Muslim control of Jerusalem so that the sultan would learn about Christ and convert to the one true faith. Conversion of Jews and Muslims is another end-time prophecy, Whalen says.

Little did that priest know that his kind of understanding of events would inspire great battles aimed at bringing forth the end of days.

Here’s how all this got started. Before the Last Supper, Jesus said to his disciple Simon, “Thou art Peter. And upon this rock I will build my church.” Peter brought Christ’s message to Rome, and he was martyred. Later, Roman bishops thought of themselves as Peter’s heirs and appointed a pope as God’s viceroy on Earth. But in the fourth century, Constantine — the first Roman emperor to convert to Christianity — moved the imperial capital to Constantinople, where bishops didn’t always bow to papal authority.

That wasn’t too big a deal back then. “Papal authority existed only on paper,” Whalen says. “For vast stretches of time, the pope was just another bishop who had a theoretical grandeur.”

Until the eleventh century. That’s when European cities grew and commerce prospered. And so did the Church. Christians gave the Vatican more money, which it used to exert direct control over individual churches and communities. As the Church grew stronger, some monks and abbots conjured ideas of what the Church’s larger role in society should be. Well-known theological reformers, such as Peter Damian and Humbert of Silva Candida, urged the Church to separate itself from society. They said clergy should not marry or have children or own property. That separation, they thought, would give the Church more moral authority and greater influence in the day-to-day lives of Christians, including secular rulers.

“There’s this grassroots movement in the eleventh century with all these reformers,” Whalen says. “And then one of them became pope — Leo IX — and a whole cadre of reformers went to Rome. They had a vision for what the world should look like and would look like.”

And as Whalen writes in his book, Dominion of God, that vision included when the apocalypse would come.

In 1054, with reformers now in the Vatican, the Latin Church demanded that Eastern Christians conform to Western rites and sacraments, such as using unleavened bread for the Eucharist. The Eastern Church refused; it preferred leavened bread. And so the two wings of Christendom officially split. Looking into this era, Whalen found that many theologians displayed an apocalyptic zeal; they thought it a travesty that Christendom had been rent asunder.

In the late eleventh century, the Church gained even more power, seizing from the German emperor the right to appoint bishops and abbots in an episode historians have written about extensively.

Click to read photo caption. ©2010 Endeavors magazine.

“What fascinated me about this time was how the reformist papacy started looking outward toward the Islamic world, the Greek Church, and the Jews,” Whalen says. In particular, reformers started talking about the Peace of God — peace among Christians.

In 1095, Pope Urban II received a letter from the patriarch of the Eastern Church, who needed help repelling Muslim Turks. Later that year, at a large gathering of church leaders and laymen, Urban II addressed violence among European Christians. “Why fight each other?” he said. “Why not turn our swords toward the infidels who are plaguing the church in the East and defiling the Holy Land?”

Historians have long known about Pope Urban II’s speech. But Whalen emphasizes the pope’s motive: little-known historian Guibert of Nogent quoted Urban II saying that Christianity should be thriving in Jerusalem; only then would the Antichrist appear and persecute the faithful — a necessary evil — before his final defeat at the end of time. Urban II then called for the First Crusade, which began in 1096. Three years later, Christian knights seized Jerusalem, its surrounding provinces, and several other Mediterranean counties and cities.

It was a stunning victory, and apocalyptic-minded reformers considered it the will of God. The prophecies were being fulfilled, they thought.

“It’s easy to see that God is on your side when things go well,” Whalen says. “But what happens when things go wrong? Well, reformers had an answer for that, too.” God was angry. And between the eleventh and fourteenth centuries, historians say, reformers found explanations for God’s wrath. Reports had reached Rome of crusaders raping Christian women, killing children, and plundering cities. Clergy were upset and made sure the pope knew how they felt. But according to Whalen’s findings, some texts reveal what the reformers were thinking. They said the End Times would come only when the Church was made pure. But as time went on, Whalen says, reformers saw the Church more and more as an intractable part of the problem.

In his book, Whalen writes that twelfth- and thirteenth-century apocalyptic thinkers began looking toward a glorious future when the Church would be hardly recognizable — no clergy, no sacraments, no church institutions at all.

“Reformers still believed in spreading the gospels around the world to bring people into one fold,” Whalen says. But they thought the Church had become too corrupt to shepherd the flock. “They thought there’d be a new spiritual leadership of monks in the future,” he says.

Joachim of Fiore, the best-known proponent of that kind of thinking, divided time into three stages — the age of the Father (from Adam to Christ), the age of the Son (from Christ to Joachim’s day), and a future age of the Holy Spirit, which would be, according to Joachim, “without war, without scandal, without worry or terror, since God shall bless it and he shall sanctify it.”

According to Whalen’s research, kings and popes found inspiration in Joachim’s description of the Greeks as the “lost sheep” who would be brought into the one true fold before the end of days. Jews would recognize Christ, Joachim wrote, and some Muslims would convert.

In 1204, Pope Innocent III quoted Joachim in a letter to Constantinople. The pope said that the successful siege of that Christian city during the Fourth Crusade was a sign of God’s hand in history because the Latin Church needed to become one with the Eastern Church.

But Joachim’s followers wrote books about how the sins and decadence of Rome would be exposed before the End Times and that the Antichrist would purge the Church of its shortcomings. “One such book was burned by papal order,” Whalen says. “But the idea didn’t go away.” Reformers more radical than Joachim took up his mantle. Peter John Olivi, for instance, called Rome “the carnal church” and advocated for major reform, Whalen says.

Whalen traced the lineage of Joachite thinkers through the fourteenth century. Most of them were more radical than Joachim and each was critical of Rome’s decadence. Yet, Whalen says that the strong papacy was able to contain rebellion among radical monks, abbots, and priests or purge them from the Church.

Until the fourteenth and fifteenth centuries. That’s when the Vatican weakened politically and European monarchs gained power, opening the door for a sort of end time the Church did not foresee.

Whalen ends his book at the dawn of the fifteenth century, by which time the influence of the apocalyptic thinkers on the papacy had waned. But reformers are forever.

In 1517 a Dominican friar named Johann Tetzel knocked on Martin Luther’s door in Wittenberg, Germany, to sell indulgences — payments to the Vatican for blessings and penance. The encounter with Tetzel inspired Luther to post ninety-five theses critical of the papacy. Number eighty-six read: “Why does the pope, whose wealth today is greater than the wealth of the richest Crassus, build the basilica of St. Peter with the money of poor believers rather than with his own money?”

Indulgences were nothing new: the Vatican had granted them to the earliest crusaders. Later, popes granted indulgences to women and others who couldn’t fight. Over time indulgences became big business, Whalen says, and the Vatican grew rich while many believers stayed poor. This did not sit well with many ordinary Christians and reformers.

“People in the Middle Ages were just as aware of hypocrisy as we are today,” Whalen says. “They knew Christ and the apostles lived lives of poverty.” Pope Leo X excommunicated Luther, but German princes and other clergy came to Luther’s aid, sparking the Protestant Reformation. Christendom would never be the same.

Whalen points out that Luther, like previous reformers, had never wanted to break from the Church. But also like his predecessors, Luther became more radical when the Vatican, in his eyes, did not respond well to calls for reform.

“Luther even called the pope the Antichrist,” Whalen says — a sure sign that the apocalypse was at hand.

Brett Whalen is an assistant professor of history in the College of Arts and Sciences.