 Why does supervenience appear to generate strict laws? When Davidson first stated the supervenience claim, he articulated it in the following terms: “there cannot be two events alike in all physical respects but differing in some mental respects” (Davidson 1970, 214)). This formulation appears to entail strict psychophysical laws of the form ‘P1 →  M1’. Davidson later came to focus on the inversion of this formulation: “if two events fail to share a mental property, they will fail to share at least one physical property” (Davidson 1995a, 266). The advantage of this reformulation is that it brings out the fact that the requisite physical differences need not be the same in each case of mental difference (see Davidson 1973a, 253–4). As Davidson says, 