Reviewed by: The Schelling-Eschenmayer Controversy, 1801: Nature and Identity by Benjamin Berger and Daniel Whistler Mark J. Thomas Benjamin Berger and Daniel Whistler. The Schelling-Eschenmayer Controversy, 1801: Nature and Identity. Edinburgh: Edinburgh University Press, 2020. Pp. xvi + 269. Hardback, £80.00. This excellent book focuses on a decisive moment in Schelling's philosophical development: his 1801 dispute with Eschenmayer shortly before publishing Presentation of My System, the inaugural text of his identity philosophy. Carl August Eschenmayer was a German physician whose Kant-inspired writings in the philosophy of nature greatly influenced Schelling, especially with respect to the doctrine of the potencies. Nonetheless, he is a marginal figure in the history of philosophy, and one might assume that this volume will only interest Schelling specialists or those concerned with the minutiae of nineteenth-century Naturphilosophie. That would be a mistake. As Berger and Whistler demonstrate, the 1801 controversy has significant implications for understanding the trajectory of German Idealism and its debates on methodology, the meaning of identity, and the place of nature in philosophy. [End Page 703] Part 1 of this volume contains translations of the two essays at the heart of the dispute, both published in January 1801 (Judith Kahl and Daniel Whistler are the translators). The essay by Eschenmayer, "Spontaneity = World Soul, or The Highest Principle of Philosophy of Nature," critiques Schelling's 1799 nature-philosophy and presents his own Fichte-inspired approach. Schelling's rejoinder is the essay "On the True Concept of Philosophy of Nature and the Correct Way of Solving Its Problems," which anticipates the new identity philosophy he would present later that year. Translations of the two thinkers' correspondence and selections from other works by Eschenmayer are included in appendices. Overall, the translations are precise and quite readable—an achievement for German texts with scientific jargon. Moreover, the translators are thoughtful in their rendering of tricky words like Verhältnis, which can mean "relation," "proportion," or "ratio" in different contexts (see xiii–xiv). Occasionally there are minor inaccuracies, but they do not detract from the texts' main arguments. What, then, are the main points of disagreement between Schelling and Eschenmayer? In the preface, the authors identify a "twofold difference" (ix). The first concerns the relationship of the philosophy of nature to transcendental philosophy. Eschenmayer follows Fichte in including the former within the latter: the "I" is ultimately responsible for nature's determinate features. By contrast, Schelling insists on the self-sufficiency of naturephilosophy and argues for its priority: consciousness and the transcendental standpoint are not original but are derived from nature (9–10). The second difference concerns the source of qualitative difference among natural phenomena. While Eschenmayer reduces quality to mathematical proportions of attraction and repulsion, Schelling argues that such a reduction amounts to explaining nature's diversity through varying degrees of density (56). The bulk of the volume (part 2) is a series of chapters on themes related to the dispute and its aftermath. Though labeled "commentaries," they are really critical essays, providing historical context and analysis while engaging with an impressive range of secondary literature. The first chapter is devoted to the construction of material qualities, the "guiding thread" of Eschenmayer's essay (83). The authors carefully trace the problem from Kant through the two philosophers' evolving conceptions of nature-philosophy leading up to the 1801 dispute. Though Schelling rejects Eschenmayer's account of quality in terms of attraction and repulsion, he is "greatly influenced" by his sparring partner's emphasis on quantitative difference in explaining quality, even adopting some of his mathematical concepts (89). The most important of these is "potency," the subject of the next chapter and one of the central concepts in Schelling's thought for the next forty years. After an account of its roots in mathematics and Eschenmayer's nature-philosophy, the authors analyze core features of potency in the 1801 Presentation, contrasting it with dynamis in Aristotle. Fundamentally, the series of potencies involves differentiation through intensification of the same underlying identity: "Life is nothing more than intensified inorganic matter" (102). The chapter concludes with a strong defense of Schelling against Hegel's charge of formalism—though it still seems to me that the schema of...