Sluicing is ellipsis in a question, leaving only a wh-phrase overt (Ross 1969), e.g.: Sally called someone, but I don't know who. Recent work on the licensing conditions of sluicing has converged on the need for a semantic approach to ellipsis licensing, where the sluiced question must be congruent to a Question under Discussion (QuD, Roberts 1996; e.g. Ginzburg and Sag, 2000; AnderBois, 2011; Weir, 2014; Barros, 2014; Kotek and Barros, To appear). In this talk, we address problems of over-generation predicted by this account, stemming from a more general concern: what is the source of QuDs, and how are they constrained?
Adopting the notion of strategy trees and super/sub-questions from Rojas-Esponda (2014) (cf Buring 2003, Roberts 2012), we propose that sluicing is licensed by the most recently raised QuD in the discourse, and not by its super- or sub-questions, nor by unrelated QuDs. We show how this proposal accounts for several test-cases that are problematic for traditional approaches, including cases of sprouting (1), Dayal and Schwarzschild’s (2010) Antecedent Correlate Harmony generalization (2–3), and contrast sluicing (4). We argue that this approach provides a natural explanation for Barker’s (2014) ‘Answer Ban:’ the observation that the antecedent clause must not resolve, or even partially resolve, the issue raised by the sluiced question.
(1) Sally left, but I don't know {why, when, in which car, with whom, ...}
(2) Joan ate a donut.
a. *Fred doesn’t know what.
b. Fred doesn’t know which donut.
(3) Joan ate something.
a. Fred doesn’t know what.
b. *Fred doesn’t know which donut.
(4) A: Did(n't) Sue call [Jack]F?
B: #I don't know who.