[3] Because expressivism claims that the function of moral language is not descriptive, it allows the anti-realist to avoid an error theory: the view that ordinary ethical thought and discourse are committed to deep and pervasive error and that all moral statements make false ontological claims.
Expressivists are united in rejecting ethical subjectivism: the descriptivist view that utterances of the type "X is good/bad" mean "You ought to do/ought not to do X".
[9] Hare's view is called prescriptivism because he analyzed moral sentences as universal, overriding prescriptions or imperatives.
Much of the current expressivist project is occupied with defending a theory of the truth of moral sentences that is consistent with expressivism but can resist the Frege-Geach objection (see below).
According to the open question argument (originally articulated by intuitionist and non-naturalist G. E. Moore), for any proposed definition of a moral term, e.g. " 'good' = 'the object of desire' ", a competent speaker of English who understands the meaning of the terms involved in the statement of the definition could still hold that the question, "Is the object of desire good?"
Many philosophers regard expressivists or noncognitivists as "the real historical beneficiar[ies] of the open question argument.
Terence Cuneo argues against expressivism by means of the following premise: It is false that, in ordinary optimal conditions, when an agent performs the sentential act of sincerely uttering a moral sentence, that agent does not thereby intend to assert a moral proposition, but intends to express an attitude toward a non-moral state of affairs or object.
[16] Proponents of expressivism are concerned to preserve the participants in ordinary moral thought and discourse from charges of deep error.