  This is not to say that analytic naturalists allow no room for empirical investigation into morality—far from it. If, for instance, an analytic naturalist were to hold that the term ‘good’ is synonymous with ‘pleasurable’, they would hold that the claim “Pleasure is good” is analytic, and knowable a priori. But the claim “It is good to help others” would be the kind of claim that is amenable to empirical investigation, in virtue of the fact that “It is good to help others” would be synonymous with “It is pleasant to help others”, and whether pleasure results from helping others is the kind of claim that can be empirically investigated. So analytic naturalists should be understood as saying that some moral claims—in particular, moral claims that state general relations between natural properties and moral properties (like “Pleasure is good”)—are knowable a priori. Synthetic naturalists claim that all moral claims are synthetic claims, knowable by empirical methods.