Johann Friedrich Blumenbach (1752-1840) is widely known as the father of German vitalism and his notion of Bildungstrieb, or nisus formativus, has been recognized as playing a key role in the debates about generation in German-speaking countries around 1800. On the other hand, Caspar Friedrich Wolff (1734-1794) was the first to employ a vitalist notion, namely that of vis essentialis, in the explanatory framework of epigenetic development. Is there a difference between Wolff's vis essentialis and Blumenbach's nisus formativus? How does this difference influence their overall understanding of the epigenetic process? The paper aims to provide an answer to these questions through the analysis of a little-known document, which contributes to shed light on a crucial chapter of the German life sciences in the late eighteenth-century, namely the decisive phase of the process that led to the formalization of biology as a unified field of inquiry at the beginning of the nineteenth century.
Keywords: Caspar Friedrich Wolff; Epigenesis; Johann Friedrich Blumenbach; Teleology.