Studies on the syntactic consequences of event type in languages have shown that Aktionsart plays a role in Universal Grammar. This book contributes to the exploration of the syntax/semantics interface by presenting a thorough comparison of event and predicate types in English and Spanish. The mapping between event and syntactic predicate types, including detransitives, is given a minimalist account based on the functional categories that embed event features and on a careful analysis of the features checked by objects. As the book delves into the theoretical issue of how parameters are characterized, it presents the most comprehensive account to date of event type phenomena in Spanish, an innovative analysis of the clitic SE and a re-definition of unaccusativity. The theory is then applied to the ongoing issues in the sentence processing literature. A proposal is made for an update of the current data in light of these latest linguistic discoveries.