Mechanistic evidence: Disambiguating the Russo-Williamson Thesis

Russo and Williamson claim that establishing causal claims requires mechanistic and difference-making evidence. In this paper, I will argue that Russo and Williamson’s formulation of their thesis is multiply ambiguous. I will make three distinctions: mechanistic evidence as type vs object of evidence; what mechanism or mechanisms we want evidence of; and how much evidence of a mechanism we require. I will feed these more precise meanings back into the Russo-Williamson Thesis and argue that it is both true and false: two weaker versions of the thesis are worth supporting, while the stronger versions are not. Further, my distinctions are of wider concern because they allow us to make more precise claims about what kinds of evidence are required in particular cases.