 According to some metaethicists  (moral non-cognitivists  or expressivists), moral claims – such as the injunction that one ought to return people’s phone calls – are neither true nor false. The same situation holds, according to some philosophers of language, for claims that presuppose the existence of something which does not in fact exist, such as the claim that the present King of France is bald; for sentences that are vague, such as ‘These grains of sand constitute a heap’; and for sentences that are paradoxical, such as those that arise in connection with the  Liar Paradox.  Let us call this thesis the gap, since it finds a gap in the class of sentences between those that are true and those that are false.