This dissertation deals with one of the central concerns of syntactic theory since Ross 1967: How local is syntax and what are the measures of syntactic locality? On an empirical level, it presents the results of three independent strands of research on German: (i) the study of reduced infinitive constructions, in particular, Bech's (1955/57) classic work on COHERENCE versus NON-COHERENCE in German, (ii) the POSSESSOR DATIVE CONSTRUCTION (PDC), with a dative nominal playing the role of both possessor and affectee, and (iii) BINDING, the conditions under which reflexive and non-reflexive pronouns may occur.

Both the PDC and binding are phenomena involving relations between two structural positions, and both are sensitive to the internal complexity of intervening material. Exploiting this sensitivity, I propose that possessor datives and binding can serve as probes for infinitival clause size. Building on Wurmbrand 2001, I provide new evidence for a distinction between infinitival complements that is more fine-grained than, and thus goes beyond, the traditionally assumed binary distinction between coherence and non-coherence.

These results provide the foundation for addressing two larger theoretical issues: the typology of clause size and what makes a given phrase-type transparent (constructed coherently) or opaque (constructed non-coherently) to grammatical interactions with elements beyond its boundaries.

Examining various clausal and sub-clausal phrase-types, in particular ACCUSATIVUS CUM INFINITIVO (AcI)-constructions, in connection with the PDC and binding, I ultimately propose Chomsky's (2000, 2001) notion of PHASE as the single determinant of locality which unifies all three of the syntactic phenomena at issue here. Just as Chomsky's (1973) SPECIFIED SUBJECT CONDITION (SSC) constrained both movement configurations and coreference possibilities, in the system I develop, phases impose the crucial locality restriction on both PD-raising and binding. However, while the opacity-inducing presence of an intervening specified subject does play an important role in my accounts of the PDC and binding, I argue that appealing to phasehood covers more ground. It captures the opacity effects triggered not only by verbal and nominal (vP and DP) domains but also by clausal and prepositional (CP and PP) domains.