That early modern Christians were fascinated, and at times obsessed, with alleged and real Jewish expertise in arcane knowledge is well known. How the exchange of secrets — defined as “intentionally concealed knowledge . . . knowable in principle” (10) — ranging from alchemy and magic to the natural sciences, the military, and politics, affected Jewish-Christian relations is, to the contrary, a much less researched topic, which Daniel Jütte investigates in this elegant and energetically erudite study, originally published in German in 2012. Focusing in particular on Northern Italy and the German-speaking lands in the sixteenth and seventeenth centuries, Jütte claims that “we underestimate the importance of secret forms of knowledge in the premodern world” (258). In fact, the trade in secrets was “central to premodern Jewish economic life” (5). Operating in the “economy of secrets” that characterized early modern Europe offered skilled Jews social and economic opportunities, which allowed them to “forge remarkable contacts with the dominant society” (7) in ways that the open exchange of information and knowledge could not. Secrecy, in other words, opened rather than closed possibilities for social relations and economic improvement.

After an introduction that illuminates the multiple contexts of the profound early modern interest in secret knowledge, Jütte offers a remarkable survey of the sort of activities that “Jewish professors of secrets” engaged in, such as alchemy, medicine, espionage, cryptography, technology, and the trade in unicorn horns. This emphasizes both the widespread involvement of Jews everywhere in the trade of concealed practical knowledge, and the extent to which early modern professional categories were blurred within the context of the economy of secrets. A separate chapter is devoted to magic, “which created zones of contact between the Christian majority and the Jewish minority in important ways” (86). Although the author relies almost exclusively on secondary sources in these two chapters, the amount of evidence he marshals is impressive. Still, the significant number of inquisitorial trials concerning Jews and magic held in the archives of the Roman Holy Office, a relevant body of sources that the author does not use, could have corroborated his argument, while drawing greater attention to the high risks that supposed Jewish expertise in arcana posed in the Italian states, a subject mentioned only in passing.

A fourth chapter, on the “complex interconnections between Jewish economic life and the early modern economy of secrets” (95), leads the way to the central section of the book, a meticulously researched and lengthy case study that convincingly reassesses the early modern Jewish “professor of secrets” par excellence: engineer, alchemist, and inventor Abramo Colorni from Mantua. The diverse and apparently incongruous activities of this colorful character (“from military inventions, to trading in curiosa and dealing in divinatory practices, to magic and card tricks” [217]), who was described either as a charlatan or a “Jewish Leonardo” in earlier scholarship, are here coherently reconstructed in light of his involvement in the early modern trade of secrets. Because of the extant sources, Jütte approaches Colorni through the lens of his relations with Christians and an investigation of his works, evaluating above all his attempts at self-presentation (it remains to be seen how Colorni was perceived by his coreligionists and by the Jewish authorities, a question that could be extended to all Jewish “traders of secrets” investigated in this book). Eager to fashion himself as a professional expert in arcane knowledge, similarly to his more famous contemporary Giovan Battista Della Porta, Colorni “propagated a systematic and scientific magia naturalis while attacking superstition” (154), but as a Jew also took advantage of King Solomon’s ideal image as the knower of all of nature’s secrets.

Jütte’s volume challenges a number of historiographical notions regarding the relationship between Jews and science. Above all, the traditional scholarly focus on Jewish contributions to the scientific world, or the lack thereof, misses “opportunities for investigating the full range of Jewish expertise in natural history, the occult, and technology, including the intersections of such knowledge with economic activity” (232). Thanks to their expertise in concealed but useful knowledge, Jewish professors of secrets played a prominent role at European courts, in alchemical laboratories, as well as in armories and workshops. Jütte repeatedly reminds us of the blurred lines between science, technology, and magic in early modern Europe, and we can only be grateful to him for this.