 What kind of explanation is at issue? As we understand matters, we are looking for a “constitutive explanation”, an account of the essential nature of the property (or properties) of being normative, or a “real definition” of the property (or of each of the properties) (Rosen 2010; also Schroeder 2005, King 1998). A non-normative example of such an explanation would be the account of the property of being an acid according to which to be an acid is to be a proton donor. The question is whether there could be a relevantly similar naturalistic account of the essential nature of the property of being normative. Or, if there is more than one such property, the question is whether there could be naturalistic accounts of the essential natures of the normativity properties.