This paper discusses the morphosyntactic properties exhibited by existential pivots such as 'a war' in (1)
(1) There was a war all summer.
In various languages such NPs do not follow general patterns of argument realization. The paper argues that they do not do so because they are not arguments, but rather the main predicates of their constructions. A compositional semantics for existential constructions is provided which builds on but differs from the analysis of Barwise and Cooper 1981, and in which pivots are predicates of domains. This analysis is argued to provide a better understanding of the morphosyntax of existential constructions than analyses based on small clauses or on unaccusativity.