  Drawing on an epistemic theory of vagueness, Krifka (2007) argues that prefixal negation always yields semantic contradictories. On this view, unhappy is literally just ‘not happy’, with the characteristic stronger understanding derived pragmatically. The incomplete cancellation of the two negators in not unhappy is taken to be a purely pragmatic phenomenon, conflating this case with that of not impossible. But the classical theory has its advantages. On that approach, un-Adj antonyms (like their morphologically simplex classmates, sad or bad) are lexical items that can constitute contraries vis-à-vis the corresponding positive. By virtue of their lexical status, they are candidates to undergo further semantic drift, unlike not Adj sequences (or non-Adj forms), as evidenced in the semantic and phonological opacity of infamous or impious. Note too that many un- and in- adjectives (unkempt, inchoate, incorrigible) lack corresponding simple bases. Furthermore, the prefix non- yields staunch contradictories (typically with objective and/or technical senses) often contrasting minimally with un-Adj or iN-Adj contraries favoring gradable and evaluative contexts: