This book is the first attempt to provide a unified account of the be-possessive syntax and its extension to the modal and the perfect constructions in Russian/North Russian within a generative framework. Apparently diverse constructions are construed as deriving from the have/be parameter, which depends on the utilization of the prepositional complementizer with a Case feature. The be-perfect structure provides an adequate environment where ergativity is encoded via verbal nominalization. The relevance of the be-perfect structure for a split ergative pattern shows that the ergative system is a syntactically conditioned phenomenon rather than a purely morphological diversity. This volume also offers the diachronic study of the be-syntax, investigating the evolution of the be-perfect and be-modal constructions, which has rarely been explored within a formal framework. Concrete scenarios are proposed for the developmental paths of the be-perfect and the be-modal constructions, based on textual evidence in old North Russian.