The subject of nonfinite clauses is often missing, and yet is understood to refer to some linguistic or contextual referent (e.g. 'Bill preferred __ to remain silent' is understood as 'Bill preferred that he himself would remain silent'). This dependency is the subject matter of control theory. Extensive linguistic research into control constructions over the past five decades has unearthed a wealth of empirical findings in dozens of languages. Their proper classification and analysis, however, have been a matter of continuing debate within and across different theoretical schools. This comprehensive book pulls together, for the first time, all the important advances on the topic. Among the issues discussed are: the distinction between raising and control, obligatory and nonobligatory control, syntactic interactions with case, finiteness and nominalization, lexical determination of the controller, and phenomena like partial and implicit control. The critical discussions in this work will stimulate students and scholars to further explorations in this fascinating field.