‘What can I say about the blood of San Gennaro, religiously preserved in Naples?’ asked physician Matthaeus Silvaticus in his renowned Pandectarum medicinae (mid-fourteenth century). To this enduring question, Francesco Paolo De Ceglia, professor of history of science at the University of Bari, has offered the most comprehensive answer to date in Il segreto di San Gennaro: Storia naturale di un miracolo napoletano, first published in Italian in 2016 (Einaudi) and now available in English translation. This book reconstructs the centuries-long intellectual, theological and political debate surrounding the blood miracle.
Notably, the English edition reverses the original title and subtitle, perhaps to assist readers less familiar with the miracle. This was not always necessary. ‘Who hasn’t heard of the miracle of San Gennaro’s blood, kept inside a glass vial in Naples?’ asked Spanish priest Louis of Granada, in the sixteenth century (p. 60). Three times a year, in Naples’s Duomo, before an enthusiastic and fervent crowd of believers, the blood of San Gennaro – housed in two small vials – liquefies (or ‘boils’, depending on the century, as De Ceglia shows). Should it fail to liquefy, terrible catastrophes befall the city, as occurred in 1980 with a devastating earthquake (for detailed statistics regarding failed liquefactions and catastrophes, see p. 246).
The ‘natural history’ is De Ceglia’s reconstruction of ‘the culture that has identified it as a miracle, to either sustain or eventually challenge it’ (p. 6), leaving readers to parse the boundary between ‘natural’ and ‘cultural’. Methodologically, the miracle is treated as a wonder with an ‘epistemic function’ (p. 7). De Ceglia combines anthropological insight – in the tradition of Ernesto De Martino – with analysis of philosophical and theological traditions that tried to make sense of the phenomenon. He anchors these texts in social and political events, though more convincingly for later centuries. With a flair for storytelling, the fine, erudite and witty prose is a pleasure to read in Italian, though occasionally dense. The translators (Manuel Romero, Alessandra Balzani, Clorinda Donato and Jaclyn Taylor) have done an excellent job. The English edition includes twenty-five images absent from the Italian version, enhancing the reader’s comprehension. The price of the English volume, however, is nearly four times higher than that of the Italian one. While this is likely De Ceglia’s most widely known book, specialists in the field will already be familiar with De Ceglia’s studies on corpses, vampires, demons and death.
Drawing on an impressive variety of sources, including paintings, chronicles, religious treatises, natural-philosophy dissertations, legends and newspaper articles, De Ceglia interrogates the mechanisms behind the miracle’s construction, and its consolidation across different social actors over more than seven centuries. The book unfolds in eight mostly chronological chapters, each brimming with revelations and enigmas. Chapter 1 recounts the story of Saint Januarius, Bishop of Benevento, who was martyred by decapitation in Pozzuoli in 305 CE. The nebulous history of the saint’s relics took a decisive turn more than a thousand years after his death, when a 1389 political chronicon first mentioned his blood and described the miracle. Chapter 2 traces the miracle’s stabilization during the fifteenth century, emphasizing the importance of its ritual calendar. The scheduled repetition of the miracle helped avoid confusion and overexposure. The interaction between the saint’s head and blood relics, brought close together during the ritual, was recognized as a prodigy rooted in the concept of martyrdom.
Chapter 3 juxtaposes Catholic and Protestant perspectives on the miracle, especially regarding cruentation cadaverum (the bleeding of a corpse in the presence of its murderer). De Ceglia presents a disenchantment narrative: Protestants sought to reduce such phenomena to natural causes (reductio ad naturam), aiming to discredit miracles and sever communication between the living and the dead, though paradoxically embracing cadaveric pharmacopoeia, which Catholics could not share. Nevertheless, the Protestant claim that San Gennaro’s miracle was a devil’s act rather than God’s could not be easily dismissed by Catholic thinkers, who found themselves caught in a logical loop within Catholicism itself.
The central chapters cover the early modern era and the eighteenth century. In Chapter 4, where the history of science takes centre stage, the focus shifts toward seventeenth-century Aristotelian natural philosophers, such as Fortunio Liceti, who interpreted the miracle according to post-Tridentine doctrine. This required them to deny fiercely that the miracle was anything but supernatural. Chapter 5 explores the institutional establishment of the three annual dates (in September, December and May), which crystallized the miracle as supernatural occurrence in the Catholic liturgical practice. Jesuits, especially from the sixteenth century onward, showed growing interest. De Ceglia convincingly characterizes Naples as an urbs sanguinis (city of blood), where multiple blood relics began to liquefy at a moment when competition among religious institutions was fierce. In Chapter 6, the miracle and its prophecies become deeply entwined with Neapolitan Weltanschauung, a process described both by sceptic Northern European travellers and by Neapolitans of all classes, including new kings eager to be accepted. Chapter 7 is the chapter of eighteenth-century enlightened disbelief. In Berlin, chemists staged experiments purporting to show that the vial’s contents were not blood, but a product of (al)chemical fabrication. Catholic defenders took these claims seriously, though no replicated substance has yet fully mimicked the phenomenon.
The final chapter brings the story to an end by tracing the miracle’s behaviour during the French occupation, the arrival of Garibaldi and the late twentieth-century scientific debates that reached the pages of Nature in the 1980s. The mystery remains unresolved. The Church, however, has since reclassified the miracle as a ‘prodigy’, perhaps to temper devotional practices that have fallen out of favour.
In mapping the evolving interpretations of San Gennaro’s miracle, the English translation of De Ceglia’s work offers readers a valuable case study in how miracles function as both epistemic and cultural artefacts, bridging devotional life and scientific inquiry while seldom failing to attract the attention of political leaders of the day.
