This is the first volume dedicated to the study of formal features and the expression of arguments within Phase Theory, the latest model of syntactic theorizing within the Minimalist Program. The collection addresses the nature of formal features and their role in the syntactic computation as well as checking mechanisms and configurations. It also investigates theoretical issues underlying the nature of syntactic arguments and their licensing (argument structure at large) and specific grammatical operations involving arguments (abstract and morphological case, empty elements, passivization, negation, and aspect). The chapters presented in this volume provide case studies from several, typologically unrelated languages. Apart from novel analyses of new as well as well-known facts, the contributions also provide interesting aspects of and challenges for Phase Theory in general, by critically exploring a number of theoretical extensions, proposing new syntactic mechanisms, and sharpening our tools for linguistic analysis.