Published online by Cambridge University Press: 14 October 2010
This paper proposes a treatment of optional prepositional phrases with a status intermediate between adjuncts and complements. The essential idea is simply that such PPs are semantically but not syntactically selected. It is argued that prepositions often assign an external theta role to a complement of the governing verb, subject to the heretofore unnoticed syntactic condition that such external arguments must be direct rather than oblique. This explains certain binding opacity effects and also greatly simplifies the subcategorization frames of verbs. The analysis is formulated in the framework of Head-Driven Phrase Structure Grammar (Pollard & Sag 1994).