In his book Catholics and Unbelievers in Eighteenth Century France (1939), the historian R.R. Palmer wrote that

on the whole, it must be confessed that the thought of the Age of Enlightenment, more than that of any equally important period in modern history, has been studied chiefly from writings which express only one side of the question.

Palmer went some way to illustrating that there was considerable intellectual opposition to the philosophes, overwhelming from Catholics, which could not be dismissed as bloody-minded obscurantism. He also illustrated that Voltaire and others, for all their purported advocacy of tolerance, were not above using underhanded methods to ruin and silence their intellectual adversaries.

Nor, Palmer held, were the philosophes’ critics necessarily closed to the many genuine intellectual advances produced by the various Enlightenment movements. This story, its antecedents, and its effects are the focus of a new book by Ulrich L. Lehner, The Catholic Enlightenment: The Forgotten History of a Global Movement.

Lehner, author and editor of several well-researched books on Catholicism and the various Enlightenments, notes that the image of religious figures being somehow opposed holus bolus to Enlightenment ideas is one that has been steadily discredited over the last 50 years. “Today,” he writes,

historians recognize that only a small fraction of Enlighteners were anti-religious; the overwhelming majority were interested in finding a balanced relationship between reason and faith.

Some were deists. A few were atheists. Yet to take just one Enlightenment—that of 18th century Scotland—many of its leading lights such as Hugh Blair, Francis Hutcheson, Gershom Carmichael, Adam Ferguson, William Robertson, and Thomas Reid were not just believing Christians but also ministers of the Church of Scotland. Self-described infidels such as David Hume were the exception.

Less attention has been given to those whom Lehner calls “Catholic Enlighteners.” Many historians of the Enlightenments, he points out, assumed that only anti-religious thinkers were enlightened; hence, by definition, “there could not be a Catholic Enlightenment.” Historians such as Palmer and Father Bernard Plongeron who suggested the contrary were for a long time a minority. Lehner, however, provides a comprehensive analysis of the Catholic Enlightenment which establishes him, I would argue, as his generation’s preeminent historian of this movement.

One of Lehner’s central themes is that the roots of Catholic Enlightenment thought are to be found in that most reforming of Church councils: the Council of Trent (1545-1563). Trent’s impact in terms of clarifying church dogmas and doctrines, curbing laxity among the clergy, implementing an extensive seminary and university reform program, and propelling the rise of dynamic religious orders (to name just a few changes) is hard to underestimate. Trent facilitated the development of a thoroughly orthodox, intellectually rigorous, and disciplined clergy; a renewed emphasis upon addressing social and economic problems; a repudiation of superstitious customs; and, perhaps most significantly, an emphasis that lay people were also called to holiness. This idea pervades, for instance, Saint Francis de Sales’ immensely influential Introduction to the Devout Life (1609).

Trent was therefore about improvement. And comprehensive efforts to better the human condition was a central leitmotif of the various Enlightenments and one to which, Lehner shows, many Catholics were naturally well-disposed. In some areas, such as enhancing women’s legal status and education, it turns out that Catholic reformers were well ahead of their Protestant and more secular-minded counterparts.

This helped create conditions for an engagement on the part of Catholic intellectuals with Enlightenment thinkers and ideas in fields ranging from philosophy and science to law and economics. Observing, for instance, the discoveries made through enhanced use of the empirical method, Catholics shaped by Trent’s reforms wanted to underscore the compatibility between faith and science. But they also desired to enhance the Church’s capacity to communicate its teachings “more widely and in a more conceptually clear manner.” That meant addressing criticisms of the Church and Catholic belief articulated by some Enlightenment thinkers.

“Catholic Enlighteners,” Lehner writes, “sought to show the public that they could successfully grapple with their intellectual counterparts and that they possessed the same intellectual abilities.” This, however, did not translate into outright rejection of every Enlightenment tenet: “Catholic Enlighteners saw some merit in the criticism and tried to refute them thoroughly while also ceding some ground.”

Thus the French Oratorian priest Nicholas Malebranche affirmed Baruch Spinoza’s claim that the universe was shaped by eternal laws underpinned by an infinite intellect, but maintained that this was actually compatible with belief in a personal God. Other Catholic thinkers addressed arguments made by Enlightenment thinkers against key Christian claims. In response, for instance, to Hume’s argument that no testimony could validate the claim of a miracle, Catholic Enlighteners such as Gabriel Gauchat politely observed that “without trust in the testimony of men, all human knowledge would vanish.”

Likewise, critical analysis of the Scriptures was not rejected out of hand by Catholic Enlighteners. Another Oratorian, Richard Simon, is a prominent example of one who found helpful aspects of Enlightenment scholars’ and Protestant theologians’ textual investigation of the Bible.

Similarly the Enlightenment argument for freedom was embraced by many Catholic Enlighteners.

The Italian cleric Fernando Galiani, an example invoked by Lehner, stressed the importance of political liberty and wrote an extensive defense of economic freedom 20 years before the 1776 publication of Adam Smith’s The Wealth of Nations. Other Catholic Enlighteners wrote of the need for toleration of groups whose religious views did not threaten the common welfare. That is obviously far from full religious liberty. Yet it marked a considerable advance in a world in which most people—Catholic, Protestant, Orthodox, and even some deists—were inclined to view the failure to embrace the dominant religion of sovereign states as close to treason.

Much of the Catholic Enlighteners’ agenda involved making the case to more skeptical minds that Catholicism’s claims were supported by reason. Catholic moral theologians of the period, for instance, emphasized that all peoples could know the moral truths contained in natural law, independently of Divine Revelation (something affirmed long ago by numerous medieval and patristic Catholic thinkers as well as Saint Paul). Politically speaking, some Catholic Enlighteners supported various social and political reforms pursued by absolutist Catholic monarchs such as Emperor Joseph II. This included significant changes to the legal treatment of the Church in their domains, which often led to conflict with a politically weakened papacy.

A particular strength of Lehner’s analysis is the manner in which he explores important differences among Catholic Enlighteners. Like their skeptical and Protestant counterparts, they did not hold monolithic views. One important cleavage was between those influenced by Jansenism (formally condemned as a heresy by Pope Clement XI in 1713) and Jansenism’s fiercest critics, the Jesuits. The subsequent theological conflict was ferocious and spanned the entire Catholic Enlightenment period. For all their differences, however, both groups were influenced by John Locke’s empiricism and Isaac Newton’s physics. This reinforced openness throughout the Church to the insights of the natural sciences which led, for instance, to Catholic missionaries, bishops, and popes endorsing and promoting the practice of vaccination.

Concerning internal church matters, Catholic Enlighteners disagreed about questions such as clerical celibacy, though, according to Lehner, most favored retention of a discipline that goes back to Christianity’s earliest centuries. While some Catholic Enlighteners were relatively hostile to particular papal claims to authority and argued for more state control over the Church to help reduce Rome’s influence, others combined engagement with Enlightenment ideas and the natural sciences with strong loyalty to Rome and firm resistance to efforts by absolutist monarchs to intervene in the Church’s internal life.

As Lehner makes very clear, the Catholic Enlightenment movement was not confined to Western Europe. Far more than previous historians of this period, he shows how it affected the entire global church. The scope of this book embraces Western, Central, and Eastern Europe, but also the Americas, China, Africa and India. Jesuit and Franciscan missionaries of the 18th century introduced to Latin America modern thinkers such as Locke and Benjamin Franklin as well as curricula stressing the natural sciences. Many of the missionaries, we learn, regularly corresponded with the European scientific community. In North America, prominent Catholics such as the Carroll family—who were in no sense theological liberals but nonetheless well-read in Enlightenment thought—actively supported the American Revolution and defended the subsequent experiment in republican government.

In China, writes Lehner, Jesuit, Franciscan, and Dominican missionaries proved more open to Confucian philosophical insights than were secular Enlightenment minds. In India and Africa, many bishops began ordaining native clergy at a time when the Spanish and Portuguese crowns were trying to restrict colonial officeholders to white Europeans. Many such clergy, educated in Rome, brought back Enlightenment political ideas to their native lands and became early and articulate critics of colonialism’s dark side.

On one question, however, indelibly associated with colonialism—slavery—Lehner states that the Church “has an ambiguous record.” Almost all Enlightenment thinkers morally disapproved of it. Yet, according to the author, they nonetheless condoned slavery and were “passive when it came to actual help.” By contrast, popes, bishops, and Dominican natural law theorists contested the very idea of natural slavery, stressed the equality of slaves and masters regarding salvation, resisted the enslavement of Native Americans, and defended the right of slaves to marry. Catholic Enlighteners were also among the first to fundamentally question slavery’s legitimacy as an institution. That said, the slave trade was not denounced formally by a pope until 1839. It was also defended by a number of theologians. Moreover, members of religious orders such as the Benedictines, Carmelites, and Jesuits owned large numbers of slaves in the Americas and had few qualms about doing so.

So what happened to the Catholic Enlightenment? Judging from Lehner’s analysis, it ended for three reasons.

One was a tension between those Catholic Enlighteners who engaged modern ideas so as to enhance Catholicism’s ability to defend its positions, and those who essentially sought to subordinate theology to more radical Enlightenment ideas as well as increase state power over the Church.

Another was the increasingly aggressive hostility towards Catholicism exhibited by late French Enlightenment thinkers such as Jean-Jacques Rousseau and Paul d’Holbach (whose atheism was deplored by no less than Voltaire). When coupled with the ultimately successful 18th century campaign pursued by Jansenists, philosophes, and sympathetic governments to suppress the Jesuit order, the result was far less conversation and much more pointed criticism of various Enlightenment claims by many formerly sympathetic Catholics.

The main reason, of course, was the sheer ferocity of the French Revolution’s assault on the Church. The destruction of churches, the wholesale looting of its property, the subjugation of its educational institutions, the torture and massacres of clergy, and the genocide of Catholic peasants in the Vendée by men claiming to be inspired by Enlightenment ideals was bound to lead many Catholics to turn away from anything associated with Enlightenment. Those Catholics who tried to maintain some type of conversation with leaders of the Revolution were generally ignored by them as well as detested by their fellow Catholics.

Not surprisingly, Counter-Enlightenment thought soon achieved ascendancy within the Church. Paradoxically, observes Lehner, the deplorable treatment of the popes by revolutionary forces and eventually Napoleon helped bolster ultramontanist tendencies among Catholics. The Church subsequently regained an inner unity that proved invaluable in the face of persecution. It also resulted, however, in what Lehner describes as a “tendency to turn theology into ideology.”

The wider significance of Lehner’s work is to challenge the notion that, between the Reformation and Vatican II, Catholicism retreated into an intellectual ghetto. Indeed, one could add that a substantive re-engagement between the Church and modernity actually began at Vatican I (1869-1870) with that council’s reiteration in Dei Filius (1870) that “there can never be any real disagreement between faith and reason” and subsequent outline of the potentially productive relationship between these two sources of knowledge. With Leo XIII’s pontificate (1878-1903), the Church began reflecting constructively upon the new economic world bequeathed by Adam Smith’s ideas and industrial capitalism. During the same period, substantive efforts were made by Leo to put distance between the Church and throne-and-altar arrangements.

In fact it would be difficult to describe any pope from Benedict XV (1914-1922) onward as entertaining knee-jerk anti-Enlightenment sentiments. Notwithstanding the scale of the assault on the Church after 1789, the conversation between Catholicism and modernity did not have to wait until Vatican II to resume.

The Catholic Enlightenment is a major contribution to ongoing efforts to show that, from its very beginning, Catholic Christianity has rarely been closed to insights into the truth attained by those of different faiths or none. As Ulrich Lehner highlights, Christianity’s engagement with modernity is never without its dangers and occasionally ends in tears. Still it is in many ways an inevitable exchange from which, he shows, the Catholic Church should never shy away.