 Non-naturalists, next, are often charged with not being able to explain what appears to be a necessary dependence of moral facts on natural facts. Normally, this dependence is explained in terms of supervenience, but in order for such an account to be compatible with the basic tenets of moral non-naturalism, it has been argued, this supervenience must, in turn, be explainable in purely non-naturalistic terms (for an overview of this debate, cf. Ridge 2018). According to Shafer-Landau (2003) (as interpreted by Ridge 2007) this problem is solved if moral and physical properties in the sense of kinds, are distinguished from moral and physical properties in the sense of tokens, or tropes. For then we can say, in analogy with what has been suggested in the debate on the causal relevance of mental properties, that although (necessarily) every moral trope is constituted by some concatenation of natural tropes, it does not follow that every moral type is identical to a natural type. This suggestion is criticized in Ridge 2007.