Christianity's original anti-science crusade: The religious order that tried to crush modernity

Long before Francis became its first pope, the Jesuit brotherhood tried to snuff out a revolutionary new theory

By Amir Alexander

Published April 13, 2014 6:00PM (EDT)

  (AP/Andrew Medichini/<a href=''>Ig0rZh</a> via <a href=''>iStock</a>/Salon)
(AP/Andrew Medichini/Ig0rZh via iStock/Salon)

Excerpted from "Infinitesimal: How a Dangerous Mathematical Theory Shaped the Modern World"

On August 10, 1632, five men in flowing black robes came together in a somber Roman palazzo on the left bank of the Tiber River. Their dress marked them as members of the Society of Jesus, the leading religious order of the day, as did their place of meeting—the Collegio Romano, headquarters of the Jesuits’ far-flung empire of learning. The leader of the five was the elderly German father Jacob Bidermann, who had made a name for himself as the producer of elaborate theatrical performances on religious themes. The others are unknown to us, but their names— Rodriguez, Rosco, Alvarado, and (possibly) Fordinus—mark them as Spaniards and Italians, like many of the men who filled the ranks of the Society. In their day these men were nearly as anonymous as they are today, but their high office was not: they were the “Revisors General” of the Society of Jesus, appointed by the general of the order from among the faculty of the Collegio. Their mission: to pass judgment upon the latest scientific and philosophical ideas of the age.

The task was a challenging one. First appointed at the turn of the seventeenth century by General Claudio Acquaviva, the Revisors arrived on the scene just in time to confront the intellectual turmoil that we know as the scientific revolution. It had been over half a century since Nicolaus Copernicus published his treatise proclaiming the novel theory that the Earth revolved around the sun, and the debate on the structure of the heavens had raged ever since. Could it be possible that, contrary to our daily experience, common sense, and established opinion, the Earth was moving? Nor were things simpler in other fields, where new ideas seemed to be cropping up daily—on the structure of matter, on the nature of magnetism, on transforming base metals into gold, on the circulation of the blood. From across the Catholic world, wherever there was a Jesuit school, mission, or residence, a steady stream of questions came flowing to the Revisors General in Rome: Are these new ideas scientifically sound? Can they be squared with what we know of the world, and with the teachings of the great philosophers of antiquity? And most crucially, do they conflict with the sacred doctrines of the Catholic Church? The Revisors took in these questions, considered them in light of the accepted doctrines of the Church and the Society, and pronounced their judgment. Some ideas were found acceptable, but others were rejected, banned, and could no longer be held or taught by any member of the Jesuit order.

In fact, the impact of the Revisors’ decisions was far greater. Given the Society’s prestige as the intellectual leader of the Catholic world, the views held by Jesuits and the doctrines taught in the Society’s institutions carried great weight far beyond the confines of the order. The pronouncements coming from the Society were widely viewed as authoritative, and few Catholic scholars would have dared champion an idea condemned by the Revisors General. As a result, Father Bidermann and his associates could effectively determine the ultimate fate of the novel proposals brought before them. With the stroke of a pen, they could decide which ideas would thrive and be taught in the four corners of the world and which would be consigned to oblivion, forgotten as if they had never been proposed. It was a heavy responsibility, requiring both great learning and sound judgment. Little wonder that only the most experienced and trusted teachers at the Collegio Romano were deemed worthy to serve as Revisors.

But the issue that was brought before the Revisors General that summer day in 1632 appeared far from the great questions that were shaking the intellectual foundations of Europe. While a few short miles away Galileo was being denounced (and would later be condemned) for advocating the motion of the Earth, Father Bidermann and his colleagues were concerning themselves with a technical, even petty question. They had been asked to pronounce on a doctrine, proposed by an unnamed “Professor of Philosophy,” on the subject of “the composition of the continuum by indivisibles.”

Like all the doctrinal proposals presented to the Revisors, the proposition was cast in the obscure philosophical language of the age. But at its core, it was very simple: any continuous magnitude, it stated, whether a line, a surface, or a length of time, was composed of distinct infinitely small atoms. If the doctrine is true, then what appears to us as a smooth line is in fact made up of a very large number of separate and absolutely indivisible points, ranged together side by side like beads on a string. Similarly, a surface is made up of indivisibly thin lines placed next to each other, a time period is made up of minuscule instants that follow each other in succession, and so on.

This simple notion is far from implausible. In fact, it seems commonsensical, and fits very well with our daily experience of the world: Aren’t all objects made up of smaller parts? Is not a piece of wood made of fibers; a cloth, of threads; an hour, of minutes? In much the same way, we might expect that a line will be composed of points; a surface, of lines; and even time itself, of separate instants. Nevertheless, the judgment of the black-robed fathers who met at the Collegio Romano that day was swift and decisive: “We consider this proposition to be not only repugnant to the common doctrine of Aristotle, but that it is by itself improbable, and . . . is disapproved and forbidden in our Society.”

So ruled the holy fathers, and in the vast network of Jesuit colleges, their word became law: the doctrine that the continuum is composed of infinitely small atoms was ruled out, and could not be pursued or taught. With this, the holy fathers had every reason to believe, the matter was closed. The doctrine of the infinitely small was now forbidden to all Jesuits, and other intellectual centers would no doubt follow the order’s example. Advocates of the banned doctrine would be excluded and marginalized, crushed by the authority and prestige of the Jesuits. Such had been the case with numerous other pronouncements coming out of the Collegio, and Father Bidermann and his colleagues had no reason to think that this time would be any different. As far as they were concerned, the question of the composition of the continuum had been settled.

Looking back from the vantage point of the twenty-first century, one cannot help but be struck, and perhaps a bit startled, by the Jesuit fathers’ swift and unequivocal condemnation of “the doctrine of indivisibles.” What, after all, is so wrong with the plausible notion that continuous magnitudes, like all smooth objects, are made of tiny atomic particles? And even supposing that the doctrine is in some way incorrect, why would the learned professors of the Collegio Romano go out of their way to condemn it? At a time when the struggle over Copernicus’s theory raged most fiercely; when the fate of Galileo, Copernicus’s ardent advocate and the most famous scientist in Europe, hung in the balance; when novel theories on the heaven and the earth seemed to pop up regularly, didn’t the illustrious Revisors General of the Society of Jesus have greater concerns than whether a line was composed of separate points? To put it bluntly, didn’t they have more important things to worry about?

Apparently not. For, strange as it might seem to us, the condemnation of indivisibles in 1632 was not an isolated incident in the chronicles of the Jesuit Revisors, but merely a single volley in an ongoing campaign. In fact, the records of the meetings of the Revisors, which are kept to this day in the Society’s archives in the Vatican, reveal that the structure of the continuum was one of the main and most persistent of this body’s concerns. The matter had first come up in 1606, just a few years after General Acquaviva created the office, when an early generation of Revisors was asked to weigh in on the question of whether “the continuum is composed of a finite number of indivisibles.” The same question, with slight variations, was proposed again two years later, and then again in 1613 and 1615. Each and every time, the Revisors rejected the doctrine unequivocally, declaring it to be “false and erroneous in philosophy . . . which all agree must not be taught.”

Yet the problem would not go away. In an effort to keep abreast of the most recent developments in mathematics, teachers from all corners of the Jesuit educational system kept proposing different variations on the doctrine in the hope that one would be tolerated: Perhaps a division into an infinite number of atoms was allowable, even if a finite number was not? Maybe it was permitted to teach the doctrine not as truth but as an unlikely hypothesis? And if fixed indivisibles were banned, what about indivisibles that expanded and contracted as needed? The Revisors rejected all of these. In the summer of 1632, as we have seen, they once again ruled against indivisibles, and Father Bidermann’s successors (including Father Rodriguez), when called to pass judgment on it in January 1641, again declared the doctrine “repugnant.” In a sign that these decrees had no more lasting effect than their predecessors, the Revisors felt the need to denounce indivisibles again in 1643 and 1649. By 1651 they had had enough: determined to put an end to unauthorized opinions in their ranks, the leaders of the Society produced a permanent list of banned doctrines that could never be taught or advocated by members of the order. Among the forbidden teachings, featured repeatedly in various guises, was the doctrine of indivisibles.

What was it about the indivisibles that was so abhorrent to the Jesuit Revisors in the seventeenth century? The Jesuits, after all, were a religious order—the greatest one of the day—whose purpose was saving souls, not resolving abstract, technical philosophical questions. Why, then, would they bother to proclaim their opinion on so inconsequential a matter, pursue it and its advocates decade after decade, and with the sanction of the highest authorities of the order, make every effort to stamp it out? Clearly the Black Robes, as the Jesuits were popularly known, saw something in this apparently innocuous thesis that is completely invisible to the modern reader—something dangerous, perhaps even subversive, that could threaten an article of faith or core belief the Society held dear. To understand what this was, and why the largest and most powerful religious order in Europe took it upon itself to eradicate the doctrine of indivisibles, we need to go back a century, to the founding days of the order in the early sixteenth century. It was during that time that the seeds of the Jesuit “war on indivisibles” were sown.

The Emperor and the Monk

In the year 1521 the young emperor Charles V convened a meeting of the estates of the Holy Roman Empire in the west German city of Worms. Only two years past his election to his high office, Charles was titular head of the Holy Roman Empire, commanding the allegiance of its princes and vast populace. In fact, he was both less and more than that: less because the so-called “empire” was in reality a patchwork of dozens of principalities and cities, each fiercely protective of its independence and as likely to oppose as to aid its imperial lord in time of need; and more because Charles was no ordinary prince; he was a Habsburg, a member of the greatest noble family the West has ever known, with possessions extending from the coast of Castile to the plains of Hungary. Consequently, Charles was not only the elected emperor of Germany, but also, by birthright, the king of Spain and the duke of portions of Austria, Italy, and the Low Countries. Moreover, in those very years, Castile was fast acquiring new territories in the Americas and the Far East, making Charles, in a phrase from the time, “the emperor in whose lands the Sun never sets.” And though Francis I of France and Henry VIII of England might have bridled at the suggestion, to his contemporaries as well as to himself, Charles V was the leader of Western Christendom.

In the winter of 1521, however, it was his fractured German empire, not his vast overseas possessions, that were chiefly on the emperor’s mind. It had been three and a half years since Martin Luther, an unknown Augustinian monk and professor of theology, nailed a copy of his Ninety-Five Theses to the door of the Castle Church in Wittenberg. The theses themselves were narrowly focused, confronting what Luther saw as an unconscionable abuse practiced by the Church: the sale of “indulgences,” which were guarantees of divine grace, absolving the purchasers of their sins and sparing them the torments of purgatory. Luther was far from alone in denouncing the sale of indulgences, which was one among many Church practices that were routinely condemned as abuses by both clerics and laypeople. Nevertheless, Luther’s open challenge to Church authorities struck a nerve with both scholars and the common people like nothing before it. Over the following months, with the aid of the newly invented printing press, the theses were disseminated all across the Holy Roman Empire, and were enthusiastically received nearly everywhere.

If this had been where things ended, then the affair would have been of no concern to Charles V. Like many in his day, Charles, too, was distressed by the more egregious practices of the Church, and he may even have felt some sympathy toward the audacious monk. But events soon acquired a momentum of their own. Alarmed by Luther’s success, his Augustinian superiors called him to account at a meeting in Heidelberg, but by the time he left, he had converted many of them to his position. When he was then summoned to Rome, he sheltered under the protection of his prince, the elector Frederick the Wise of Saxony, who arranged for a hearing for him in Germany instead. In an effort to discredit this irksome critic, Church authorities sent the Dominican professor Johann Eck of Ingolstadt, a professional debater and theologian, to confront Luther. The two met for a public debate in 1519, in which Eck skillfully maneuvered his opponent into admitting to clear heresies: that divine grace is granted to believers through faith alone, not through the sacraments of the Church; that the Church is a purely human construct and holds no special power to mediate between men and God; and that its supreme head, the Pope, is fundamentally an impostor. Luther made no apologies for his beliefs; Eck denounced him as a heretic.

Unfortunately for Church leaders, this designation did nothing to slow down the zealous Luther. In 1520 he published three treatises that outlined his basic doctrines in deliberate defiance of established teachings. No longer a critic, he was now a rebel, openly calling for the overthrow of the Church hierarchy and institutions. His influence continued to spread, first in Wittenberg, then in Saxony, and soon clear across Germany and beyond. Everywhere, it seemed, Luther was acquiring followers in all classes and stations of life—men and women, nobles and peasants, country people and city dwellers—all of whom saw him as a leader of a religious awakening that would displace the ossified and corrupt Church of Rome. At long last growing alarmed at the fast-deteriorating situation, Pope Leo X excommunicated Luther, but by this time the drastic action had little effect. Luther’s teachings were spreading like wildfire throughout German lands.

It was at this time, spurred by the threat of religious schism, that Charles V entered the fray. Two centuries later the French philosophe Voltaire would mock the empire as “neither Holy, nor Roman, nor an Empire,” but to Charles, his realm was holy indeed. As the secular leader of Christendom, and a devout Christian himself, he saw it as his sacred duty to preserve the Church and the spiritual unity of his people. Though Holy Roman emperors have for centuries vied with popes for supremacy in Europe, their squabbles on occasion resolved only by open warfare, it was clear to Charles that the former could not do without the latter.

After all, it was the Pope who, since the days of Charlemagne, crowned emperors, and the Church that gave legitimacy and purpose to the office of emperor. The notion of an empire without a Roman Church, or an emperor without a pope, was unthinkable to Charles. To put his domains in order, and stop the spread of the Lutheran heresy once and for all, he called for a “diet”—a meeting of the estates of the empire.

When the diet convened in the city of Worms in January of 1521, Charles sent Luther a summons to appear before the emperor and the estates and account for his actions. Despite Charles’s guarantee of his safety, many of Luther’s friends cautioned him against placing himself in his enemies’ power and advised him not to go. Nevertheless, in April, Luther arrived in the city and was promptly called before the assembled notables. There he was immediately presented with a list of his heretical doctrines and asked to acknowledge them and recant. Luther was surprised; he had expected to be allowed to argue his case, and was unprepared for the swiftness of the attack. He managed only to ask for a day’s reprieve to consider the matter, and Charles, the chivalrous Christian emperor, granted the request. But the next day, Luther was ready. He willingly acknowledged his beliefs, even in the face of hostile questioning and fierce denunciations. When pressed to recant, he answered calmly, “Here I stand; I can do no other; God help me; amen.”

With these words Luther ensured the failure of Charles’s mission to stamp out heresy in his German lands, but he also did much more: he sealed the fate of Western Christendom. For over a thousand years the Roman Church had reigned supreme in western Europe. It had witnessed the rise and fall of empires, invasion and occupation by infidels, heresies large and small, plague and pestilence, and ruinous wars of king against king and emperor against pope. Through it all, the Church had survived, thrived, and expanded its reach until, by the sixteenth century, its dominion stretched from Sicily to Scandinavia and from Poland to Portugal, and to beachheads in the New World. From baptism to last rites, the Roman Church oversaw the lives of Europeans, giving order, meaning, and purpose to their existence, and ruling on everything from the date of Easter to the motion of the Earth and the structure of the heavens. To the people of western Europe, regardless of nation, language, or political allegiance, the fabric of life itself was inextricably bound to the Roman Church.

But when Luther took his stand at the Diet of Worms, this spiritual and cultural unity came to an abrupt end. By proudly proclaiming his heretical beliefs, he renounced the authority of the Roman Church and led his followers along a new religious path. By openly defying both Pope and emperor before a public gathering of the great men of the empire, he burned his bridges, and eliminated any chance of reconciliation. What up to that point could have been viewed as an internal rebellion within the Church now became a schism in which two rival faiths confronted each other in open hostility. On the one side stood the followers of the old Church; the Pope; and his secular sword, the emperor. On the other, the adherents of the new “Protestant” Church, which claimed direct descent from the ancient apostolic church and rejected the Roman faith as a monstrous aberration. The spiritual unity of the West was shattered with one blow, and any realistic hope of healing the rift through conciliation or threats was at an end. Luther and his followers refused to concede their errors or surrender to the might of the empire. Consequently, they had to be subdued by force of arms.

Decline Into Chaos

For the next thirty-four years of his reign, Charles V tried to accomplish precisely that. Though all too often distracted by threats from his European rivals and the Ottoman sultan, he nevertheless carried on a consistent campaign to suppress the cancer of Protestantism that was spreading through his lands. But it was too late. Not only was the new faith gaining adherents by the day among the populace, but great princes of the empire were also rallying to Luther, and establishing his church in their territories. First were the electors of Saxony, Frederick the Wise and his successors, who had been Luther’s protectors from the beginning. Next was Albrecht of Hohenzollern, grand master of the Teutonic knights, who refashioned himself as the first duke of Prussia and laid the foundations of what would become the greatest Protestant power in Germany. The elector Philip of Hesse followed suit, as did the margrave of Brandenburg, the dukes of Schleswig and Brunswick, and many smaller potentates of the empire. The great imperial cities (Nuremberg, Strassburg, Augsburg) also sided with Luther, broke with the Pope, and established their own reformed churches. By the mid 1520s it seemed nothing could resist the rising tide of Lutheranism.

If the rupture of the empire wasn’t bad enough, it soon became clear the dissolution of Christendom would not stop there. In the early 1520s a cleric at Zurich Cathedral named Huldrych Zwingli began preaching fiery sermons denouncing the wickedness of Rome and advocating doctrines even more radical than Luther’s. Within a few years he rallied Zurich, and then the neighboring Swiss cities of Bern and Basel, to his cause. Zwingli’s death in a battle against the Catholic forest cantons of the Swiss Confederacy in 1531 brought a temporary halt to the spread of his radical vision, but by the late 1530s a new beacon of reform had emerged in Geneva. In 1536, John Calvin launched his long campaign to make Geneva into a shining example of the purest Protestant faith, and of upright public and personal morality. Over the following twenty years, Calvin managed to transform Geneva into a strict theocracy in which no individual action was beyond the scope of religious oversight or censure. And though the example of Geneva might appear unattractive to us, reminiscent as it is of some of the darker theocratic regimes of our own day, contemporaries judged it differently. Calvin’s city was glorified as the “city on the hill,” a shining example of what could be achieved through religious fervor, moral rectitude, and hard work. Aspiring reformers from across Europe flocked to the city to learn from Calvin how it was done, and to spread his teachings to their native lands. Thanks to the example of Geneva, Calvin’s brand of Protestantism, set down in his Institutes of the Christian Religion, became the most dynamic and influential movement of the Reformation from the 1540s onward. Even without the princely support that had institutionalized Luther’s reforms, Calvin captured millions of converts, from France and England in the west to Poland and Hungary in the east.

Meanwhile, disasters kept piling up for the Roman Church, as not only cities and territories but entire kingdoms were lost to Protestantism. In 1527 the Swedish king Gustavus Vasa adopted Lutheranism and, over the following years, established it as a national church. Less than a decade later, Frederick I, a north German prince who had become king of Denmark, drove out the bishops, abolished the monasteries, and installed Lutheranism as the state religion. Since Norway was at the time under Danish suzerainty, and Finland was a province of Sweden, this made all Scandinavia into the Protestant stronghold it remains to this day.

In England, welcoming the Reformation was initially more of a pragmatic than a spiritual choice. Henry VIII had stood faithfully by the Roman Curia in the early years of the Reformation and even authored an anti-Lutheran treatise that earned him the title Defender of the Faith from Pope Leo X. But as the years went by, Henry grew restless as his wife, the Spanish princess Catherine of Aragon, failed to provide him with a male heir. Resolved to replace Catherine with her charismatic lady-in-waiting Anne Boleyn, he appealed to Pope Clement VII to annul his marriage. Clement, eager to maintain close relations with his royal champions, would likely have granted Henry’s request, had it not been for the fact that the queen was Charles V’s maternal aunt. Charles made it clear that any attempt to cast Catherine aside would be a personal affront to his honor, and Pope Clement VII could not defy his chief protector. He denied the petition, prompting Henry to sever ties with Rome, marry Anne, and declare himself the head of an independent “Church of England” in 1534.

Henry had no interest in the teachings of the continental reformers, and he intended only to replace the authority of the Pope with his own. Nevertheless, once the English church broke with Rome, the trend toward Protestantism proved irreversible. Under Henry’s son, the boy king Edward VI (1547–53), the English reformation veered toward radical Protestantism, only to reverse course under Edward’s half-sister (and Catherine’s daughter) Mary I (1553–58), who restored Catholicism in her tumultuous five-year reign. It was only when Anne’s daughter, Elizabeth I (1558–1603), ascended the throne that Protestantism was established as the state religion once and for all. Under the Thirty-Nine Articles of 1563, the Church of England retained many of the outward forms of the Roman Church that were favored by Henry, including the office of bishop, the sacraments, and the worship in grand and lavishly decorated churches and cathedrals. Doctrinally, however, the Church of England looked not to Rome but to Geneva, adopting the core teachings of John Calvin. To the Holy See, England was irretrievably lost.

As the Reformation spread, it soon became clear that religious truth was far from the only thing at stake. With the Pope denounced, the emperor ignored, and all the established authorities questioned and ridiculed, the entire social order came under scrutiny, and the threat of revolution hung in the air. Respectable reformers such as Luther and Calvin, and the conservative kings and princes who backed them, struggled mightily to contain the revolutionary passions set loose by the Reformation, but not always successfully. As early as 1524 the peasants of southern Germany rose in revolt against their princes, demanding greater freedoms and a greater say in the rule of the land. They declared themselves followers of Luther, believing that his overthrow of the spiritual authority of the Roman Church was but a prelude to the overthrow of the social and political order it supported. The socially conservative Luther, however, was horrified at what he saw as a profound misunderstanding and misuse of his doctrines and fiercely denounced the uprising in a tract, Against the Murderous, Thieving Hordes of the Peasants. Though the uprising was crushed within the year by the combined forces of Catholic and Protestant princes, the fear that religious reformation might spell social revolution had already taken root.

The dread of social upheaval continued to haunt the Reformation as more and more reformers and would-be prophets openly questioned the established truths and challenged the authority of the powers that be. Many were peaceful, such as the reformer of Strasbourg Martin Bucer, or the saintly wanderers Caspar von Schwenckfeld and Sébastian Franck. But others were not. Thomas Müntzer was an early follower of Luther, until he broke with him over Luther’s embrace of the princes’ power and the existing social order. In 1524, Müntzer joined the peasants’ uprising, preaching to his followers that the end of days was at hand and calling for the blood of princes. He was captured in 1525, tortured, and killed, but his legacy was still at work ten years later, when a group of radical Anabaptists took control of the city of Münster in northwestern Germany. Unlike the mainstream reformers, whose churches included all members of a community, the Anabaptists insisted that only they were the elect, the true church of God, to the exclusion of all others. At Münster they showed just how dangerous such a doctrine can be when it gains possession of earthly power. Under the leadership of Jan Bockelson of Leyden, the Anabaptists imposed a reign of terror in the city, killing or driving out anyone who stood in their way. When Münster’s former Catholic bishop, backed by the Lutheran elector of Hesse, laid siege to the city, Bockelson declared himself the Messiah, abolished private property, and instituted polygamy. In 1535 the forces of the bishop and the prince finally overcame the fierce resistance of Bockelson’s fanatical followers, and exacted a bloody revenge on the Anabaptists and anyone remotely suspected of association with them. But across Europe, fear of an impending collapse of all social hierarchy and order only deepened.

To many Europeans in those years, it seemed as if the demons of hell had risen from the underworld to spread misery and confusion upon the land. The old Church that had provided meaning, solace, and certainty to its members since time immemorial was being torn apart by an ever-increasing number of competing creeds. Every day seemed to bring more news of lands in the grip of religious turmoil, with every truth challenged and every certainty gone. The rupture of the Church was followed by political division, as Catholic and Protestant princes faced each other across the religious divide. And beneath the religious and political division lurked the nightmare of a social revolution that would sweep away the entire social order, the only one the people of that time had ever known. It was a time of strife and chaos, and to most Europeans one of debilitating confusion and uncertainty: With all old certainties challenged or discredited, and new ones announcing themselves by the day, how was one to know the difference between Truth and Error? Between the path to heaven and the path to hell?

The institution that, in the eyes of most Europeans, was charged with providing the answers and resolution to these questions was, inevitably, the Papacy in Rome. As the Pope was vicar of Christ on earth and spiritual leader of Western Christendom, it was his lands and his people that were either lost in confusion or gripped by the alien certainties of sectarians and schismatics. It was therefore the duty of the Pope to step into the breach, arrest the progress of the Protestant heresy, and return unity, order, and certainty to Christendom. Sadly for the Roman Church, however—catastrophically, even—the men who occupied the seat of St. Peter during those years were signally ill equipped to deal with the crisis that confronted them.

In many respects, the popes of the early sixteenth century were impressive men. Scions of leading Italian families, they were intelligent and highly cultured, and earned a place in history as the greatest patrons of Renaissance art. Popes Julius II (1503–13), Leo X (1513–21), Clement VII (1523–34), and Paul III (1534–49) commissioned paintings, frescoes, and sculptures by Michelangelo, Rafael, and Titian; churches and palaces from architects Sangallo and Bramante. They are responsible for some of the greatest works in the Western tradition, such as St. Peter’s Basilica and Square and the ceiling of the Sistine Chapel. But faced with the greatest crisis in the history of the Church, they found themselves helpless. Competent administrators though they were, they possessed neither the broad vision nor the spiritual authority required to confront the challenge of Protestantism.

The problem was that the Renaissance popes were not, first and foremost, leaders of Christendom, but rather Italian princelings, whose loyalties were primarily to their families and clans. Julius II belonged to the powerful della Rovere clan of Rome, Leo X and Clement VII were both members of Florence’s ruling Medici family, and Paul III a scion of the ancient Tuscan Farnese family, soon to become the dukes of Parma. For each of these clans, having one of their own elevated to Pope was not only a tremendous honor but also an opportunity to amass wealth and power that might never be repeated. Popes were expected to take care of their own, to lavish their relatives with territories, titles (both secular and ecclesiastical), gifts, and incomes. Fully aware that they would never have obtained their high station without the sponsorship of their families, the popes readily obliged, making the reign of each Pope a race against time to accumulate as many possessions and titles for his family as possible. It was a sorry spectacle of nepotism and greed reminiscent of some of the most corrupt regimes of the developing world in our own day. It hung like a malodorous cloud around the Holy See, and undermined any effort by the Pope to exercise spiritual and moral authority.

Moreover, in addition to being nominal heads of Christendom and patriarchs of greedy and acquisitive families, Renaissance popes were also the rulers of a substantial territorial state in central Italy. In their efforts to consolidate and expand their possessions, the popes became key players in the cutthroat politics of the Italian peninsula, making use of all the means at their disposal—from diplomacy to warfare to outright treachery—to advance their interests. So notorious were they for their amorality and ruthlessness in Italian politics that it was Cesare Borgia, nephew to Pope Alexander VI (1492–1503) and Alexander’s chief military commander, who served as Machiavelli’s model of a cunning and brutal prince.

The popes’ active engagement in Italian power struggles not only undercut their spiritual standing, but also hamstrung them politically. In their efforts to protect their domains, the popes had to contend with the rising power of the national states of France and Spain, both of which sought to dominate the Italian peninsula, and each of whom possessed military might and resources on a scale that could never be matched by an Italian prince. The only hope of maintaining the independence of the Papal States was to play the two kingdoms against each other, never allowing either one to gain a permanent victory. The popes managed this delicate dance quite successfully for several decades, albeit at the expense of the people of Italy, who suffered repeated invasions and counterinvasions by their mightier neighbors. But disaster finally struck in 1527, amid one of the periodic wars between Charles V, in his capacity as king of Spain, and Francis I of France. Charles’s troops, who had not been paid in months, mutinied, and sacked the city of Rome; the murder, rape, and looting went on for weeks. Pope Clement VII escaped the Vatican just in time, and holed up in the nearby fortress of Castel Sant’Angelo as the carnage swirled around him. He ultimately surrendered to the emperor, paid a ransom for his own life, and conceded extensive territories to Spain. The humiliated and much-diminished Pope was to remain effectively a client princeling of the emperor for years to come.

The upshot of all this was that when confronted with the challenge of the Reformation, the Renaissance popes had no answer. Leo X first attempted to use the most tried-and-true weapon in the papal arsenal by excommunicating Martin Luther, but this had little effect. The pleasure-loving Medici prince simply did not possess the moral stature to face down the upright Luther, and his pronouncements carried little weight. The next option for the popes was to rely on the military might of the emperor to bring the schismatics to heel, and Charles was more than willing to take on this role. The popes, however, from Leo X onward, worried that throwing their hat in with the empire meant abandoning the strategy of playing off the Habsburgs against Valois of France. Calling on Charles would effectively end the independence of the Papal States, and reduce the Pope’s temporal power to nothing. So, as Charles V struggled for decades to suppress the Protestant heresy and restore unity to Christendom, he did so with either the grudging support of the Holy See or, just as often, its open enmity. To contemporaries, it seemed that the popes would rather see all Christendom torn to shreds than surrender even a sliver of their power in Italy.

In 1540 the fires of the Reformation were still spreading unchecked through the domains of the Roman Church, and lands that had been under the sway of Rome for centuries were falling away one by one. The commonality of faith and ritual that had unified Western Christendom was replaced by a cacophony of competing creeds, each denouncing the others as impostors or worse. As chaos, war, and subversion ruled the land, the Pope proved helpless to put out the fire, but was as intent as ever on amassing titles and incomes for his relatives and protecting his territorial interests. With schism on the ground and corrupt leadership at the top, any objective observer of the European scene in 1540 would likely have concluded that the days of the ancient Church of Rome were numbered.

But on September 27 of that year, at the height of the storm, Pope Paul III took a small administrative step that seemed to bear little relation to the great events of the day: he approved a petition from a group of ten priests to form a religious company dedicated to serving the Pope and the Church. Though hardly noted at the time, it may have been the single most important step taken by the Papacy to save the Roman Church from dissolution. In his bull announcing the new order, Paul also approved the name requested by the group for their new association: They called it the Society of Jesus.

Excerpted from "Infinitesimal: How a Dangerous Mathematical Theory Shaped the Modern World" by Amir Alexander, published in April 2014 by Scientific American / Farrar, Straus and Giroux, LLC. Copyright © 2014 by Amir Alexander. All rights reserved.

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