It is widely held, even among nonnaturalists, that the moral supervenes on the natural. This is to say that for any two metaphysically possible worlds w and w′, and for any entities x in w and y in w′, any isomorphism between x and y that preserves the natural properties preserves the moral properties. In this paper, I put forward a conceivability argument against moral supervenience, assuming non-naturalism. First, I argue that though utilitarianism may be true, and the trolley driver (...) is permitted to kill the one to save the five, there is a conceivable scenario that is just like our world in all natural respects, yet at which deontology is true, and the trolly driver is not permitted to kill the one to save the five. I then argue that in the special case of morality, it is possible to infer from the conceivability of such a scenario to its possibility. It follows that supervenience is false. (shrink)

Moral language displays a characteristic duality. On the one hand, moral claims seem to be similar to descriptive claims: To say that an act is right seems to be a matter of making an assertion, thus indicating that the speaker has a moral belief about which she can be correct or mistaken. On the other hand, moral claims seem to be different from descriptive claims: There is a sense in which, by claiming that an act is right, a speaker indicates (...) that she is inclined to perform the act, to want others to perform it, and to react with praise towards those who do it. Hybrid theories maintain that utterances of moral sentences have both a descriptive and a practical linguistic function. In this thesis, I investigate how a hybrid theory can best accommodate the descriptive and the practical aspects of moral language. I evaluate and criticize the way that existing hybrid theories have proposed to explain the duality of moral language. The main arguments against these views are that they either: fail to accommodate the way that the practical or attitudinal import of moral claims vary across different contexts and linguistic environments; or that they fail to show how the practical or attitudinal import is reliably inferred by interlocutors in virtue of general communicative principles. I develop and defend a new hybrid theory called ‘dynamic descriptivism’. This theory accommodates the duality of moral language by appeal to the way that moral utterances affect a dimension of communication which consists of the shared assumptions that interlocutors mutually assume to mutually accept. Moreover, I discuss a problem which has affected a wide range of theories of moral language – including existing hybrid theories – which is the problem of explaining what it is that interlocutors disagree about when they disagree about matters of morality. I argue that that dynamic descriptivism offers new resources for solving this problem. (shrink)