This dissertation examines two information-structural phenomena, Givenness and Focus, from the perspective of both syntax and pragmatics. Evidence from English, German and other languages suggests a "split" analysis of information structure--the notions of Focus and Givenness, often thought to be closely related, exist independently at two different levels of linguistic representation. Givenness is encoded as a syntactic feature which presupposes salience in prior discourse and either (1) prevents prosodic prominence (in languages like English and German), or (2) drives syntactic movement (in languages like Italian). On the other hand, Focus, which introduces strong prosodic prominence and a contrastive interpretation, exhibits none of the expected properties of a syntactic feature, and is therefore analyzed quite differently. I argue that Focus is the result of purely pragmatic principles which determine utterance choice in the face of grammatical optionality. The syntactic and phonological systems often generate multiple possible formulations of an utterance, and communicative principles can be invoked to explain the correspondences between certain kinds of discourse contexts and certain patterns of linguistic form. The application of communicative principles to problems of utterance choice is modeled mathematically using the tools of game-theoretic pragmatics. From this perspective, utterances are taken to be strategically chosen in order to maximize communicative effectiveness. Ultimately, the strong differences between Focus and Givenness emphasize a methodological point: both syntactic and pragmatic perspectives are necessary to fully determine the space of possibilities in natural language. Neither perspective should be ignored. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]