An understatement opens the synopsis on the back jacket of this collection of essays: ‘Auctorem fidei is neither the most well-known nor the most studied of the decisions of the Catholic magisterium in the modern era.’ Nevertheless, this book is a great gift, and not just to a narrow range of specialists. The fruit of a 2016 colloquium in Paris titled, ‘From Jansenism to Modernism: the Bull Auctorem fidei (1794), Pivot of the Roman Magisterium’, this volume is relevant to a wide swath of historians and students of early modernity, especially those interested in the cultural, theological and ecclesio-political development of modern Catholicism.

Auctorem fidei, promulgated by Pope Pius vi, condemned eighty-five propositions of the (in)famous Synod of Pistoia of 1786. The condemnation of the synod of a small Tuscan diocese may seem like a rather parochial affair, but this synod, supported as it was by Peter Leopold, grand duke of Tuscany and younger brother of the Habsburg emperor Joseph ii, was a momentous challenge to papal authority and the ecclesio-political status quo on the eve of the French Revolution. It was – by self-conscious desire – a dress rehearsal for a church-wide Gallican-Jansenist reform of Catholicism, and the ‘nearest to victory that Enlightened Catholicism came’ (to quote S. J. Miller). As such, the Pistoian synod and its lengthy published Acts and decrees caused a sensation in Catholic Europe, and drew curious and even sympathetic attention from Protestant observers. The bishop of Pistoia-Prato, Scipione de’ Ricci (1741–1810), was a Florentine noble and a figure of international standing in the networks of burgeoning and increasingly radical Catholic reform circles. Given the almost total shipwreck of these reformist hopes in the aftermath of the Revolution and especially in the wake of Napoleon's reconciliation with the papacy through the 1801 Concordat, it is easy to read back and minimise the importance and power of these counter-currents in Catholicism. After all, we all know how the story ends.

Thus, the traditional view of Auctorem fidei is that it closed a chapter in history, by finally burying a morose, hyper-Augustinian movement. While this collection of essays sheds further light on the history and significance of seventeenth- and eighteenth-century Jansenism, its real strength – as the title suggests – is in furthering our understanding of the importance of Auctorem fidei for the development of nineteenth-century ‘intransigent’ Catholicism and its ‘Modernist’ foil. While this line of inquiry is certainly not without precedent – the immense erudition of Bruno Neveu and Pietro Stella, among many others, points in this direction – the new research in this volume further establishes Auctorem fidei and the legacy of anti-Jansenism in the centre of nineteenth-century struggles between Church and State, Catholicism and Liberal culture and politics (for example, through the Index and marriage legislation), and the construction of ultramontanism and the modern papal magisterium.

After a helpful introduction by the editors, the volume opens with three essays that concern the roots of the Pistoian ideas condemned in Auctorem fidei and that bull's polemical context. In chapter i, Simon Icard shows that Auctorem fidei §1's condemnation of the synod's fundamental claim that a ‘general obscuration’ of the truth afflicted the contemporary Catholic Church (brought on by scholasticism, Jesuit chicanery and hyper-papalism) was in fact an idea intrinsic to Jansenism, and not only a response to subsequent generations of rejection and condemnation at the hands of French and Roman authorities. Next, Sylvio Hermann de Franceschi – whose superabundant output in early modern ecclesiastical history is a crucial resource for scholars – tackles the polemical context of §76 of the bull, which censured the Pistoian disdain for scholasticism (in favour of ‘positive’ theology). Wolfgang Mager's contribution in a third chapter, ‘Laïcat et pouvoir du ministère ecclésiastique’, explores the backdrop of the 1727 Council of Embrun's deposition of an anti-Unigenitus French bishop as the entry point for laity – crucially, avocats – into a debate which to that point had been mainly clerical (p. 54). The Synod of Pistoia's claim that the Church's power is purely spiritual are shown to have roots in French lay resistance to the enforcement of Unigenitus (pp. 64–5). Present in this ferment was a critical spirit, even a ‘prodrome des Lumières’ (p. 70).

Next, Gérard Pelletier opens chapter iv with a useful overview of the congregations in Rome which produced the bull (pp. 88–103). But Pelletier's contribution is of particular interest for considering the long ecclesio-political afterlife of Auctorem fidei as a tool of the ultramontane papacy (pp. 103–12). The bull, so sweeping in its condemnations not only of the Jansenist roots of the Synod of Pistoia but of a host of ‘modern’ eras, was put to great use in the age of the Syllabus, in Pius x's anti-Modernist crusade and even up to the eve of Vatican II, for example in Pius xii's condemnation of liturgical reform agendas deemed hasty or primitivist.

The final five chapters are concerned with the long reception of Auctorem fidei. Mario Rochini illustrates the broad nexus of religious and political implications raised by the bull in the Lombard-Venetian context. In chapter vi, Grazia Grasso explores defences of Bishop Ricci against papal attack. Grasso sheds light on Ricci's Genoese ally Eustachio Degola, a liberal Jansenist seeking not only to restore true religion but to reconcile Catholicism with Republicanism and democracy (see esp. pp. 140–3). Jean Dubray's work in chapter vii highlights the relationship between two of the most fascinating dissident Catholics thinkers in Revolutionary era Europe – Ricci and Henri Gregoire, bishop of the French ‘Constitutional’ Church which defied the pope and defended an interpretation of the principles of 1789. Rémy Hême de Lacotte, in chapter viii, takes us from ‘antigallican polemic’ to ‘the affirmation of intransigent Catholicism’. This fascinating exploration of the use of Auctorem fidei in religious and ecclesio-political controversy in the first half of the nineteenth century is essential reading for anyone interested in the rise and eventual triumph of ultramontane Catholicism. Lacotte's research shows the surprising conclusion that the mid-1850s is in fact the ‘apogee of the diffusion of the bull’, at least for polemical purposes. In chapter ix, Jean-Baptiste Amadieu's exploration of the use of Auctorem fidei by the nineteenth-century Index for literary censures illustrates the incredible elasticity of the bull in the hands of ecclesiastical censors.

The conclusion by Philippe Boutry offers a compelling synthesis of the contributions, which, taken together, show Auctorem fidei as ‘the most concerted, most elaborate, and the most considered response of the papacy on the advent of the modern State and on the Revolution itself in their religious substance’ (p. 235). The 1850 French translation of the bull by Bishop (later Cardinal) Clément Villecourt is included in an appendix. This fascinating collection of well-written, erudite essays convincingly casts Auctorem fidei not as the end of the wearisome theological debates brought on by Jansen's Augustinus, but as a transition (or ‘pivot’) from the early modern magisterium to the modern, infallible papal magisterium which dominated Catholic thought and practice in the nineteenth and early twentieth centuries as a bulwark of counter-Revolutionary and then anti-‘Modernist’ Catholic thought.