In the 1984 preface to Cells into Organs: The Forces that Shape the Embryo, Yale embryologist John Trinkaus (‘Trink’) argued that, “‘molecular’ does not necessarily mean ‘analytical’ nor, by contrast, does ‘cellular’ or ‘histological’ necessarily imply ‘descriptive.’” Trink was reacting to the rising dominance of molecular genetic methods in the study of development, aptly encapsulated by his former PhD student, Albert Harris: “To the molecular types, a cause is a molecule or a gene. To explain a phenomenon is to identify genes and characterize proteins… A molecule is an explanation: a force is a description; to argue otherwise brings pity, at best.” Although a genetic explanatory paradigm is predominant in biology for good empirical reasons, increasing attention has been paid to how physical processes can explain development. This involves an appeal to generic features that are not unique to biological entities (e.g., shear forces due to fluid flow). Finding ways to integrate or combine generic and genetic explanatory strategies is difficult because apportioning causal responsibility among different types of causes requires a common currency. John Stuart Mill recognized this long ago in his discussion of the composition of causes and “the intermixture of effects,” but his solution relied on ascertaining the effect of each cause in isolation. After reviewing extant philosophical models for integration, I use two ideas—temporal sequence juxtaposition and actual difference making—to formulate a new approach that exploits an idealization in Mill’s methods: the mediating process between cause and effect is treated as irrelevant. My analysis helps to illuminate the resurgence of generic approaches and accounts for why this kind of integration may not always be palatable to developmental biologists because it can narrow the scope of generalizations secured for each mode of causation separately. Additionally, my analysis illustrates the value of philosophy for collaboratively achieving explanatory goals in ongoing empirical inquiry.