Meta-ethical theories are best viewed as explanatory accounts of what value and obligation are. Intuitionism takes the ontological commitments of moral discourse at face value; its most prominent competitors, the various versions of naturalism and non-cognitivism, are reductive (and in some cases eliminative) programs. A good reduction must meet certain conditions of adequacy: rough extensional equivalence, compatibility with firm results in science and the rest of philosophy, relative simplicity, and, of course, explanatory power. A good metaethical reduction must explain (among other things) aspects of logical form, the phenomenon of reason-giving, and the socalled 'dynamic' character of moral language.
This paper is about this last condition of explanatory adequacy. A major complaint of non-cognitivists is that naturalistic accounts of value and obligation fail to accommodate, let alone to explain, the non-assertive speech act potential of sentences containing moral terms. The complaint has played a pivotal role in non-cognitivist polemics, but it is not entirely clear what the structure of the argument is. In this paper I attempt to spell it out explicitly, to isolate the crucial assumptions which motivate it, and then to show just how weak the argument is. There may be many problems with the various naturalistic programs, but failure to accommodate the dynamic aspects of moral language is not one of them.
The argument I have in mind can be viewed as a variation on Moore's wellknown open-question argument. Hare's formulation is representative: Now our attack upon naturalistic definitions of 'good' was based upon the fact that if it were true that 'a good A' meant the same as 'an A which is C', then it would be impossible to use the sentence 'an A which is C is good' in order to commend A's which are C; for this sentence would be analytic and equivalent to 'an A which is C is C'. Now it seems clear that we do use sentences of the form 'anA which is C is good' in order to