 If “good” were synonymous with some naturalistic predicate “X”, then this would be obvious on reflection to every competent speaker. Hence there would be some question of the form “Are X things good?” which would not appear to be open to competent speakers, since an understanding of the words involved would suffice for an affirmative answer. Given (1.4), there is no such question; hence “good” is not synonymous with any naturalistic predicate “X”.