Materialism, Lebenskraft and the limits of science: metaphysical vitalism in post-Kantian scenarios

Kant’s legacy in the history of life sciences has notoriously included a critique of the use of soul and “vital force” (Lebenskraft). In this paper I focus on a less-known side of this legacy, i.e. Kant’s late critique of vital materialism and its impact on early and mid-19th century German science and philosophy. I show that Kant considered materialism as a kind of metaphysical hypothesis since the 1760s and pointed out that it was empirically impossible to distinguish it from different hypotheses such as monadology. This is a first example of an argument on the intrinsic instability of materialism that will be reframed in neo-Kantianism. Then I focus on Kant’s essay on Samuel Sömmering (1796), sketching the elements of Kant’s program for life sciences. I connect Kant’s program to Alexander von Humboldt’s turn from vital force to physicalism in the late 1790s, and to the anti-metaphysical and physicalist trend in the epistemologies of Hermann von Helmholtz, Friedrich Lange and Emil du Bois-Reymond. One final example of the Kantian legacy is the critique of Ernst Haeckel’s monism by du Bois-Reymond and Erich Adickes. In a final section I argue that this tradition provides a vantage point to reconsider contemporary debates over materialism and panpsychism.