Abstract

Biochemical kinds present an interesting case study in the philosophical literature on natural kinds and functions, as they fall between chemical kinds, defined by their intrinsic microstructural properties, and biological kinds, which involve functional and evolutionary considerations. Here we examine how the distinct chemical and functional properties of biochemical kinds are unified, as well as their identity criteria. We contend that unification principles are crucial for explaining the clustering of properties shared by members of natural kinds and for establishing identity criteria for such kinds. We consider whether there are specific properties that characterize biochemical kinds. This entails investigating the relationship between biochemical functions and structure. We focus on proteins, particularly on vitamin B12, as a representative example of a biochemical kind. We conclude that if there are unification principles for biochemical kinds, these principles exist at the level of biochemistry itself. This supports the naturalness of biochemical kinds as genuine categories and provides identity conditions for such kinds.