In 1990, Alan Kors published Atheism in France, 1650–1729: The Orthodox Sources of Disbelief as the first of what was intended to be a two-volume project on the emergence of atheism in a country whose philosophes were largely reputed as the most anti-clerical and “secularizing” in eighteenth-century Europe. In contrast to much of the scholarship of the time, Kors argued in it that, in the period from the death of René Descartes to the discovery of the atheistic manuscript of the abbé Meslier (1650–1729), “the seemingly boundless theistic confidence of a culture, its ostensible sense of the utter unthinkability of atheism, was unraveled by its own hands, that is, by its own teachings, debates, tensions, and rivalries” (Princeton University Press, 1990, p. ix). Twenty-six years later, Kors, the Henry Charles Lea Professor of History at the University of Pennsylvania, has returned with two additional volumes to complete his work on the topic: Naturalism and Unbelief in France and Epicureans and Atheists in France (Cambridge University Press, 2016). Although each of the books stands alone as a self-contained study, they are connected by Kors's overarching argument that atheism emerged out of the philosophical and theological debates of decidedly orthodox and theistic intellectuals in competition with each other.

Naturalism and Unbelief in France, the second in the series, provides further credence, weight, and specificity to the argument that Kors advanced in Atheism in France. Kors focuses on categorical naturalism, or the “elimination of God and the supranatural from an understanding of the reality in which humanity found itself” (5). In seventeenth-century Europe, Christians of all varieties agreed that a transcendent God created and sustained the natural order. They considered categorical naturalism to be the main ideological content of atheism. At first, categorical naturalism existed entirely in the works of the ancients. Kors points out that these classical texts were abundant and easily accessible within the learned community in France, but their arguments for a world devoid of a transcendent Creator were largely dismissed as implausible. What awoke early modern French intellectuals to the “danger” of categorical naturalism was, in fact, the fiercely contested debates between proponents of France's three dominant systems of natural philosophy: Aristotelian Scholasticism, Cartesianism, and Malebranchism. The debates focused on a variety of issues, including the definition of God, the creation of the world, and the presence of evil. Within these intellectual contests, the most pointed means by which writers denigrated their opponents was by building a case that revealed how the opposing philosophical system led to categorical naturalism and thus the philosophical content of atheism—a process Kors labels reductio ad naturalismum. Thus, for example, Aristotelians labelled Cartesian mechanism as a naturalism that removed God from an active role in sustaining the natural world and described Malebranche's definition of God as “Being in general” as the atheistic conclusion that God was simply another name for nature. In this rhetorical battle—waged in pamphlets, treatises, and learned journals—decidedly theistic philosophers gave shape to the specter of atheism and convinced their audience of the reasonableness of categorical naturalism. Kors points out that these polemical battles involved misrepresentation, for few writers, in fact, believed their opponents to be “atheists.” Their attacks rested on the claim that their opponents' systems did little to dissuade the hypothetical atheist. In the crossfire of accusations and harsh criticisms, however, they made a case for the intellectual potency of categorical naturalism.

Naturalism and Unbelief in France is tremendously well-researched, and Kors analyzes the often complicated and abstruse intellectual arguments of seventeenth- and eighteenth-century philosophers and theologians with nuance, ease, and at times even humor. One gets the sense that Kors has read every piece of natural philosophy published in France during this period, so voluminous are the examples and evidence that he presents. He clearly distills the arguments of early modern theologians and deftly analyzes the contexts within which these debates took place. Indeed, the book has value as an indispensable reference for intellectual historians looking for a primer on any number of early modern thinkers.

Kors's argument hinges in many ways on his reading of some of Francophone Europe's most important learned journals: the Journal des sçavans, the Jesuit Journal de Trévoux, and the Nouvelles de la République des lettres, among others. Kors claims that these journals reviewed and summarized philosophical works that were otherwise inaccessible for the wider literate public, fomenting many of the controversies that divided theistic writers. Indeed, Kors claims that the debates over naturalism “were played out before a rapt audience” (212) and that the journals were the key to reaching the “reading public” (237). The extent and composition of this reading public, however, is left unspecified. Kors's focus remains on the content of the debates and the ways in which they made manifest the specter of atheism.

As a work that uncovers the learned world of seventeenth- and eighteenth-century France, Kors's Naturalism and Unbelief in France is an unequivocal success. An important and valuable companion to his Atheism in France, it should be required reading for anyone studying the intellectual history of early modern France. It is an impressive book well worth the twenty-six-year wait.