This is an important book that should be read not just by historians of Catholicism and the eighteenth century but also by journalists and pundits wanting to understand the Catholic Church. From the outset, Ulrich Lehner makes a clear and persuasive case that the contemporary Church, from the Second Vatican Council to the reforms of Pope Francis, owes a vast unacknowledged debt to the eighteenth-century reformers of the Catholic Enlightenment. Furthermore, it is Lehner’s contention that many of our most cherished Enlightenment ideals—including state religious toleration and the freedom to marry for love—originate not in the ‘secular’ Enlightenment thought of Voltaire and Rousseau but in the writings of now forgotten Catholic thinkers, many of whom were priests, monks and nuns.

In this comparatively short survey of what is truly a vast subject, Lehner takes the reader on a breathless tour of the eighteenth-century Catholic world, from Europe to the Americas and from Africa to India, revealing the thought and work of enlightened Catholic reformers between around 1690 and the early years of the nineteenth century. It is a very different Catholic world from what many readers might imagine, and Lehner’s outstanding achievement is to illuminate the diversity and vitality of Catholic thought. The book deals with the Catholic contribution to developing ideas of political toleration; the contribution of Catholic women to the Enlightenment; Catholic Enlightenment outside of Europe; changing Catholic attitudes towards the supernatural; the Catholic Enlightenment’s contribution to the theology of sainthood; and Catholic opposition to slavery. Lehner highlights the key contribution of English Catholics to the global Catholic Enlightenment at several points in the book, most notably in his excursus on Thomas White, Augustine Walker, Cuthbert Wilks, Joseph Berington and John Lingard (p. 16).

Lehner successfully demonstrates that Catholic Enlightenment thinkers attained a stature and a sophistication of argument equal to the celebrated anti-clerical enlighteners—such as Nicholas Bergier, the indefatigable Catholic critic of Rousseau. Catholic enlighteners, perceiving the papacy as an obstacle to progress, forged alliances with kings and princes. However, Lehner notes that ‘regalists’ such as the Josephinists in the Austrian Empire ‘naively entrusted the sovereign with all power’ (p. 35) over reform of the Church, and the result was royal decrees which ‘hastily and without sensitivity’ proscribed practices dear to the faithful (p. 37)—a situation reminiscent of the hurt caused in some quarters by the implementation of Vatican II. However, greater state control of the Church did have some benefits, such as the constraints placed on the Portuguese Inquisition in 1769 to ensure the rights of Portuguese subjects were respected (p. 34). Poland’s brief experiment with a constitution enshrining religious freedom between 1791 and 1793 (pp. 63–7) definitively demonstrated that toleration by a Catholic state was possible.

Lehner’s book does not shy away from the complexities of the Catholic Enlightenment, particularly the ambiguous phenomenon of Jansenism. Whilst Jansenists were on the one hand the antithesis of the Enlightenment in their profoundly pessimistic evaluation of human sinfulness, on the other hand they were deeply committed to rigorous application of the critical faculties. Jansenism was responsible for a resurgence of biblical scholarship and gave birth to modern redaction criticism. These complexities are only just beginning to surface as historians finally turn their attention to the Catholic Enlightenment, yet scholarly prejudice against enlighteners who did not share an anti-clerical agenda means that crucial thinkers are being neglected.

In his chapter on slavery, Lehner draws attention to Catholic abolitionists such as Pierre Joseph André Roubaud and Henri Grégoire, although he notes that the Papal States retained galley slaves throughout the eighteenth century, and even tried to discourage the conversion of Muslim slaves to Christianity owing to fear that conversions would provoke Muslim regimes into imposing anti-Christian laws (p. 187). Jesuits in colonial Maryland, although they attempted to treat their slaves better than private owners, failed to perceive the injustice of slavery because they reacted against abolitionism as a ‘liberal Protestant movement’ (pp. 190–1). This failure seems to have been general in the Catholic world, where criticism of the mistreatment of slaves was widespread but outright abolitionism depressingly rare.

One concern about Lehner’s approach is an assumption which emerges at several points in the book that Scholasticism existed in opposition to Enlightenment thought. In fact, several Catholic thinkers whose methods were profoundly Scholastic—Thomas White among them—reached novel conclusions. However, Lehner does acknowledge that Spanish Scholastics were responsible for insisting on the importance of a free choice of spouse (p. 82). A lot more work is needed to trace the relationship between late Scholasticism and the Enlightenment, especially in Spain and Portugal. Surprisingly, too, there is no recognition of the importance of Alexander Pope, who in spite of expressing himself in poetry was one of the central influential figures of the European Catholic Enlightenment.

So what became of the Catholic Enlightenment? Lehner’s conclusion that Catholicism retreated into a defensive ‘intellectual ghetto’ (p. 12) after the French Revolution seems amply justified, but so also does his contention that the Modernists and then the Catholic reformers of the late twentieth century would not have been able to advance the ideas they did without the intellectual background of the Catholic enlighteners. To give just one example, Irish Augustinian Alexander Kenny’s description of Protestants as ‘our dear separated brethren’ found its way into the conciliar document Unitatis Redintegratio of 1964 (pp. 48–9). By uncovering the remarkable lost world of liberal, de-centralised eighteenth-century Catholicism, Lehner undermines the claims sometimes made by theological conservatives that Vatican II borrowed from liberal Protestantism. Without doubt, Lehner’s ground-breaking book is essential reading for everyone studying the Enlightenment. It should not be sidelined merely as a history of one religious response to the Enlightenment, but rather received as a hugely significant contribution to our understanding of the history of ideas.