  It has been suggested (Dreier 2004) that Ayer faced a particular difficulty in defending this brand of non-cognitivism; the combination of affirming a redundancy theory of truth with the denial that moral claims can be true looks suspicious. Although the two views are not incompatible (Ayer denied that moral claims were assertions, and the redundancy of the truth-predicate held only for assertions), the tension between the two is symptomatic of the worry that moral claims have so many of the features of truth-evaluable assertions that one has to be unjustifiably revisionist in construing them as non-meaningful. They are, after all, typically expressed in indicative sentences, and people appear to dispute moral claims. This latter point Ayer did respond to: moral disagreements were, he (and Stevenson) claimed, either genuine disputes about non-moral facts, or simply not genuine disagreements.  (For an examination of the trouble that moral disagreement makes for emotivism, see Smith 1986.) There was, however, a further, more troubling, point about the role of moral terms in arguments: moral terms can be used in arguments in which the moral term appears in a conditional, and so is not there contributing to the expressive force of the utterance, so not expressing any emotion of the speaker. This latter point has been developed into a line of reasoning (called the “Frege-Geach” problem) against expressivism in general.  The problem for the expressivist is to make sense of simple arguments such as the following: (1) If John killed Jane, he did something wrong. (2) John killed Jane. So (3) John did something wrong. The argument appears to be valid, and so not to involve any ambiguity, but the moral term can be construed as having expressive force only in (3), not in (1).  Expressivism, and so emotivism, seems to introduce an unwarranted equivocation into the argument.