Mechanisms and principles: two approaches to scientific generalization

Many philosophers have explored the extensive use of non-universal generalizations in different sciences for inductive and explanatory purposes, analyzing properties such as how widely a generalization holds in space and time. In the present paper, we concentrate on developmental biology to distinguish and characterize two common approaches to scientific generalization—mechanism generalization and principle generalization. The former approach seeks detailed descriptions of causal relationships among specific types of biological entities that produce a characteristic phenomenon across some range of different biological entities; the latter approach abstractly describes relations or interactions that occur during ontogeny and are exemplified in a wide variety of different biological entities. These two approaches to generalization correspond to different investigative aims. Our analysis shows why each approach is sought in a research context, thereby accounting for how practices of inquiry are structured. It also diagnoses problematic assumptions in prior discussions, such as abstraction always being correlated positively with generalizations of wide scope.