  Perhaps unsurprisingly, the Open Question Argument so understood still faces an impressive battery of objections. Perhaps the meaning of a predicate is not as transparent to competent users of the predicate as Moore implicitly assumes. For example, some have argued that competence with a predicate consists in being disposed (for the most part) to use the predicate only in ways that are consistent with certain “platitudes” in which the predicate figures (see, e.g. Jackson and Pettit 1995). A correct definition of the term might then be understood as one that best explains those platitudes. On this sort of account a competent user of moral terms might respect the platitudes but not recognize the theory that best explicates those platitudes even if presented with it. An analogy with grammar illustrates the point. Let us suppose that competent speakers are ones who are disposed (for the most part) to follow certain grammatical rules but they might not recognize those rules as valid when presented with them. The question, “I know the sentence violates this rule but is it ungrammatical?” might therefore seem to them to be an open one and there need be no mystery in this. The same might be true in the moral case. The non-naturalist might respond to this by arguing that if the proposed “platitudes” are substantial enough to fix the reference of moral terms to some natural property then the platitudes themselves are vulnerable to an Open Question Argument. The analogy with grammar might seem to break down at just this point. For there seems to be much more room for intelligible moral disagreement amongst competent judges in spite of agreement about everything else than there is for grammatical disagreement amongst competent judges in spite of agreement about everything else.