Michael Bennett McNulty

In his Metaphysische Anfangsgründe der Naturwissenschaft, Kant claims that chemistry is a science, but not a proper science (like physics), because it does not adequately allow for the application of mathematics to its objects. This paper argues that the application of mathematics to a proper science is best thought of as depending upon a coordination between mathematically constructible concepts and those of the science. In physics, the proper science that exhausts the a priori knowledge of objects of the outer sense, only motions and concepts reducible to motions can be legitimately coordinated with mathematical constructions. Since chemistry can neither achieve its own a priori principles of coordination nor be reduced to the coordinated doctrine of motion, it is a merely improper science.

Kant’s denial that psychology is a properly so-called natural science, owing to the lack of application of mathematics to inner sense, has garnered a great deal of attention from scholars. Although the interpretations of this claim are diverse, commentators by and large fail to ground their views on an account of Kant’s conception of applied mathematics. In this article, I develop such an account, according to which the application of mathematics to a natural science requires both a mathematical representation and a metaphysical validation for the positive use of this representation to achieve a priori knowledge about nature. The second condition—that of metaphysical validation—has been overlooked in the literature. I show that psychology’s falling short of natural scientific propriety consists not in our lacking sufficient mathematical tools for the representation of inner states, according to Kant. After all, we can represent the mere temporality of inner states with the line and their intensities with numbers. Rather, the problem is that metaphysics does not validate the further use of such mathematical entities for the achievement of a priori knowledge about inner phenomena.

Kant’s preoccupation with architectonics is a characteristic and noteworthy aspect of his thought. Various features of Kant’s argumentation and philosophical system are founded on the precise definitions of the various subdomains of human knowledge and the derivative borders among them. One science conspicuously absent from Kant’s routine discussions of the organization of knowledge is chemistry. Whereas sciences such as physics, psychology, and anthropology are all explicitly located in the architectonic, chemistry finds no such place. In this paper, I examine neglected passages from Kant’s corpus as well as texts regarding chemistry that Kant himself read in order to unveil his views on the definition of chemistry and its relations with the other sciences. These considerations reveal chemistry to be the science that studies the changes of matter into new kinds. Yet Kant idiosyncratically believes that such a change requires an infinite division of matter, effected by chemical forces. Although this understanding of chemical change dovetails with Kant’s dynamical, continualist theory of matter, it implies that chemistry cannot be reduced to physics. Thus, although chemistry stands alongside empirical physics as an applied natural science in Kant’s architectonic, it remains a distinct, independent science.

Since his Metaphysische Anfangsgründe der Naturwissenschaft was first published in 1786, controversy has surrounded Immanuel Kant’s conception of matter. In particular, the justification for both his dynamical theory of matter and the related dismissal of mechanical philosophy are obscure. In this paper, I address these longstanding issues and establish that Kant’s dynamism rests upon Leibnizian, metaphysical commitments held by Kant from his early pre-Critical texts on natural philosophy to his major critical works. I demonstrate that, throughout his corpus and inspired by Leibniz, Kant endorses the a priori law of continuity of alteration as a truth of metaphysics, according to which all alterations in experience must occur gradually through all intervening degrees. The principle thus legislates against mechanical philosophy’s absolutely impenetrable atoms, as they would would involve instantaneous changes of velocity in impact. This reveals the metaphysical incoherencies in mechanical philosophy and leaves Kant’s own dynamical theory of matter, grounded on material forces, as the only viable approach to physical explanation. Subsequently, I demonstrate that Kant nevertheless made conceptual space in his system for the theoretical consideration of mechanical explanations, which makes manifest one of the positive roles that the faculty of reason can play with respect to natural science.