This paper explores the nature of the underlying representation of a sentence, that representation formulated to make explicit the semantic structure of a sentence as a description of an event. It argues that the typical conception of an underlying representation as a predicate-argument representation, exemplified in systems of case and thematic relations, must be modified. An underlying representation must include semantic relations between noun phrases as well as the predicate-argument relations of noun phrases to a verb. An examination of instrumental with will be used to motivate and justify this revision. In particular, an account of instrumental with requires the introduction of the control relation, a relation between two noun phrases.
