 However, the real difficulty with Russell’s error theory and the one which probably weighed with Russell himself, seems to be this. Given Russell’s theory of meaning, he can make sense of non-existent properties but not non-natural predicates. At least, he cannot make sense of predicates that are not definable in terms of things with which we are acquainted. Thus on the assumption that we are not acquainted with goodness (which we obviously cannot be if there is really no such thing), and on the assumption that “good” cannot defined in terms of the things with which we are acquainted (which seems pretty plausible if is not equivalent to any naturalistic predicate) then we cannot even understand the predicate “good”. At least, we cannot understand it, if it is construed as a descriptive predicate whose function it is to denote a property (whether real or non-existent).