Sorting out left-nested conditionals

Abstract

Left-nested conditionals — those with another conditional in the antecedent — have largely been ignored in the semantic and philosophical literature. When discussed, they are usually treated as marginal or even ill-formed, even though linguistic theories of conditionals predict that they should be readily interpretable. This paper attempts to explain why they are special, and to draw out consequences for how they can be used to inform semantic theories of conditionals. Using a number of diagnostics, I show that bare left-nested conditionals are preferentially interpeted as premise conditionals. Premise conditionals are syntactically and semantically distinct from the hypothetical conditionals that the semantic literature has focused on, and they show severe restrictions in terms of the discourse contexts in which they can occur. Left-nested conditionals show the same behavior on this and a number of other diagnostics, including overt markers in Japanese and German. The paper concludes with a brief discussion of how these puzzling patterns could be explained from various theoretical perspectives, and some methodological lessons.