Natural phenomena are fundamentally law governed on Kant’s account. Any appearance of lawlessness in nature is only the result of our ignorance, and this is true whether we consider the inanimate or animate world (Jäsche Logik, IX 11). However, Kant also holds that there is an important difference between the physical and biological realms. He famously argues that the progress made in physics by Newton’s formulation of the laws of motion could never be achieved by the discovery of equivalent laws in biology (Kritik der Urteilskraft, V 400). On Kant’s account, organic phenomena must be considered according to a regulative principle of purposiveness, indicating the ‘lawfulness of the contingent’ (Kritik der Urteilskraft, V 404).
My aim in this paper is to examine the conception of biological law that emerges from Kant’s account. I argue, first, that the lawfulness of organic phenomena should be understood by analogy with rational purposiveness. According to Kant, biological lawfulness is construed on the model of the normativity of reason. I suggest, furthermore, that the relation between lawfulness in physics and biology is analogous to the relation Kant ascribes to the laws of nature and reason. On both sides of the analogy, two irreducible types of law are required for a complete account of reality. The resulting proposal will show, finally, how Kant’s account relates to contemporary discussions in philosophy of science, including current debates about the connections between evolutionary theory and rational choice theory.