This book is a cross-linguistic investigation of resumptive pronouns and related phenomena. Pronominal resumption is the realization of the base of a syntactic dependency as a bound pronoun. Resumption occurs in unbounded dependencies, such as relative clauses and questions, and in the variety of raising known as copy raising. Processing factors may also give rise to resumption, even in environments where it does not normally occur in a given language. A new theory of resumption is proposed that is based on two key assumptions, one theoretical and one empirical/typological. The first assumption is that natural language is resource-sensitive (the Resource Sensitivity Hypothesis); this is captured through the use of a resource logic for semantic composition. The second assumption is that resumptive pronouns are ordinary pronouns in their morphological and lexical properties, based on typologically robust observations (McCloskey's Generalization). The theory is formalized in terms of Glue Semantics for semantic composition, with a Lexical-Functional Grammar syntax. The theory achieves a novel unification of hitherto heterogeneous resumption phenomena. It unifies two kinds of resumptive pronouns that are found in unbounded dependencies --- one kind behaves syntactically like a gap, whereas the other kind does not. It also unifies resumptive pronouns in unbounded dependencies with the obligatory pronouns in copy raising. The theory also provides the basis for a new understanding of processing-based resumption, both in production and in parsing and interpretation.