Problems for anti‐expressivism
When is a reductio ad absurdum conclusive? One might have thought that a view which implies that commands are true or false would thereby stand refuted. Not so, according to Frank Jackson and Philip Pettit (1998). They acknowledge that one of their arguments implies that orders are true or false, but deny that this is a reason for rejecting it! This is in itself curious enough to invite discussion of their paper, which deals with metaethical expressivism, a theory which is of great interest already in its own right. In the authors' account, expressivism conjoins two theses, one negative, one affirmative. The negative thesis is that ethical sentences do not report and thus are neither true nor falsel; the affirmative thesis is that ethical sentences express attitudes. The problem for expressivism, as the authors see it, is that, contrary to what expressivists tend to take for granted, ethical sentences cannot express attitudes without reporting them. When a sentence is used to express an attitude, it cannot but be a report as well, and hence true or false. Thus expressivism lapses into incoherence: its negative thesis is that ethical sentences are neither true nor false, but its affirmative thesis, that they express attitudes, cannot hold unless they are true or false. Argument is now called for in order to establish this case against expressivism. The authors support their view, that ethical sentences cannot express attitudes without reporting them, by relying on Locke's theory of language, and begin with his observation that our use of words is conventional (Locke, 1975: 405, 53.2.2). We enter into tacit or explicit agreements to use particular words for particular things. The question next raised is whether linguistic expressions can be conventional signs intentionally used, which yet generate sentences that lack truth-value (1998: 241). The authors give a negative answer, arguing that we cannot become parties to such linguistic conventions unless we know what things an expression is to be used for. Locke wrote 'Words being voluntary signs, they cannot be voluntary signs imposed by him on things he knows not ...they would be signs of he knows not what, which is in truth to be the signs of nothing'. The authors continue: