The structure and interpretation of non-restrictive relatives: Evidence from relative pronoun pied-piping

In this paper, we investigate the structure and interpretation of English nonrestrictive relative clauses, also often called appositive relatives and sometimes supplemental relatives. We propose that in non-restrictive relatives, relative pronouns are interpreted in situ within the pied-piped constituent at LF, using RoothHamblin alternative computation (Hamblin, 1973; Rooth, 1985, 1992, a.o.). Evidence comes from the presence of intervention effects in RPPP; intervention effects (Beck, 2006; Sauerland & Heck, 2003, a.o.) can be used to diagnose regions of alternative computation (see Kotek & Erlewine, to appear; Erlewine & Kotek, 2014). The proposal here has the consequence that non-restrictive relatives are fundamentally proposition-denoting (Del Gobbo, 2007) in contrast to restrictive relatives which are property-denoting. Our proposal helps explain two differences between restrictive and non-restrictive RCs in English. First, non-restrictive relatives must use relative pronouns whereas restrictive relatives also have a that/∅ complementizer option. The relative pronoun strategy must be used in non-restrictive relatives to arrive at the propositional denotation. Second, RPPP in non-restrictive relatives can be substantially larger than in restrictive relatives. This is due to the semantics of Rooth-Hamblin alternative computation, used to interpret relative pronouns in non-restrictive relatives, which is insensitive to syntactic barriers such as islands, although it is susceptible to intervention effects.