This dissertation considers the various ways in which Chaucer explores three distinct, though related, theoretical issues posed by the development of English as a literary vernacular: namely, the nature of translation, the construction of textual memory, and the relationship between reading and ethics. Chaucer's use of translation as a means of rhetorical invention is deeply connected to medieval technologies of memory; Chaucer's poetry not only explores the theoretical possibilities of these activities, but also offers different perspectives on the relationship between right reading and right action. By analyzing works from each stage of Chaucer's poetic career, I demonstrate that these theoretical concerns are fundamental to Chaucer's art. In the early dream-visions, Chaucer experiments with the use of rhetorical and mnemonic loci as, literally, places -- an experiment that results in brilliant ekphrastic moments and a uniquely architectural poetics. With regard to the Troilus and Criseyde, I discuss Chaucer's dramatization of the problems posed by translation, focusing on his development of two English neologisms to convey the term "ambiguity" which also serve to engage the linguistic and philosophical history of polysemy. The problem of ambiguity, in turn, raises the twin questions of intention and interpretation, the questions that most inflect the activity of textual mediation. The Troilus is presented as the translation of a Latin, secular text, but the problem of textual mediation becomes highly vexed when it is addressed with regard to sacred materials. In order to examine Chaucer's dramatization of the problems of biblical translation, I set the Miller's Tale against the Parson's Tale and the Retraction. The Parson's Tale and the Retraction encourage a return to the discussion of the relationship between texts, memory, and ethics. Tracing out the progression of Chaucer's poetic thought in this way yields an appreciation of his poetry as profoundly philosophical, and it becomes clear that, as a poet, Chaucer understood both the great potential and the great risks inherent in the development of a language.