How is contraction not possible here?

Abstract

While how-questions typically elicit information about manner or instrument, English how-questions have an additional, largely unnoticed interpretation: they can be used (often rhetorically) to express surprise that the proposition under how holds at all (How is Chili's still open?) While these "propositional how-questions" freely allow negation, they do not allow neg-contraction (?*How isn't Chili's open yet?). I propose that Neg-to-C raising is blocked because it would enable Neg to (undesirably) scope over a covert VERUM operator in C that contributes to the 'surprise at the true-status of p' reading.