Abstract

I discuss genetic causation and explanation with the aim of improving our conceptualization of the relationship between genes, environment and phenotype. I then utilize this discussion to illustrate, test and elaborate certain philosophical accounts of causation and explanation . The central theme is the population-relativity of causal claims. ;I begin with an explication of 'genetic trait'. All traits have both genetic and environmental causal factors, so more must be said than that genetic traits are those caused by genes. The central sense of 'genetic' is this: a trait is genetic iff genetic differences account for the difference in the trait-variable between individuals in the actual population. Such an assessment involves the cause/condition distinction, is relative to a particular population, and is misleading as a representation of the causal processes in the individual. Nevertheless, this population-relativity is shown to be implicit throughout genetic analysis. ;Underlying this is the fact that what we typically explain are not traits per se, but differences between traits; explananda implicitly involve comparisons with some contrast case. Viewing explanations in this way has a number of important consequences: It shows how an explanation citing only one factor can nevertheless be complete. It helps to delimit the role of pragmatic factors in explanation. It exposes a problem for the theory of probabilistic causality which emerges in non-dichotomous cases. I elaborate a number of consequences of what I believe should be viewed as a central paradigm of explanation: explanation of the difference. ;Another important parallel drawn between the biological and philosophical perspectives is this: the limitation of the population-relative genetic concept and the resulting need to ask further questions is shown to be reflected in Salmon's move from a empirical reference class approach to a more thoroughgoing causal approach to explanation