A bound pronoun in the subject position of a finite embedded clause renders the clause boundary relatively transparent to relations ordinarily confined to monoclausal, control, and raising configurations. For example, too / enough -movement structures involving a finite clause boundary are degraded in sentences like * This book is too long [for John to claim [that Bill read ___ in a day]] but improved when the finite clause has a bound pronominal subject as in ? This book is too long [for John 1 to claim [that he 1 read ___ in a day]] . This bound pronoun effect holds across a wide range of phenomena including too / enough -movement, tough -movement, gapping, comparative deletion, antecedent-contained deletion, quantifier scope interaction, multiple questions, pseudogapping, reciprocal binding, and multiple sluicing; we confirm the effect via a sentence acceptability experiment targeting some of these phenomena. Our account has two crucial ingredients: (a) bound pronouns optionally enter the derivation with unvalued ϕ-features and (b) phases are defined in part by convergence, so that under certain conditions, unvalued features void the phasal status of CP and extend the locality domain for syntactic operations.