Von Baer, the intensification of uniqueness, and historical explanation

This paper aims to uncover the explanatory profile of an idealized version of Karl Ernst von Baer's notion of individuation, wherein the special develops from the general. First, because such sequences can only be exemplified by a multiplicity of causally-related events, they should be seen as the topics of historical why-questions, rather than initial condition why-questions. Second, because historical why-questions concern the diachronic unity or genidentity of the events under consideration, I argue that the von Baerian pattern elicits a distinctive response to such questions, wherein we are inclined to simultaneously affirm and reject the temporal unity of these events. I buttress this claim by considering non-biological expressions of the von Baerian principle, drawn from institutional history and literature. In the second half of the paper, I consider the implications of my findings for ontogenetic and phylogenetic sequences. I argue that the explanatory profile of von Baer's principle neatly describes the distinctive speciation events that characterize deep metazoan phylogeny, as described by Stuart Newman. I also argue that parallel considerations should move us to accept a sense in which ontogenetic stages are not diachronically unified.