  Nevertheless, philosophical worries about mental causation persist. Theoretical and commonsensical considerations leading us to think the mind or mental events cause behavior should also make us think that they do so as mental, i.e., in virtue of their mental  properties. Properties figure in causal relations (Kim 1973; Mackie 1974, ch. 10; Armstrong 1989, pp. 28–9; Ehring 1997). Drop a square paperweight into soft clay and it will produce an impression. The shape of the impression can be traced to the shape of the paperweight, the depth of the impression to the mass of the paperweight. Here shape and mass are “causally relevant” or “causally efficacious” properties. In particular, they are relevant to certain properties of the impression. By contrast, other properties of the paperweight, such as its color or value, appear to be irrelevant to producing this kind of impression. Or consider a soprano who sings a high note, thereby shattering a glass. The sound, we can suppose, has a meaning—a semantic property—but it is the sound’s acoustic properties that are operative in producing the shattering; the semantic properties play no causal role, at least not with respect to this effect (Dretske 1989).