The late Middles Ages saw the development in Europe of increasingly complex, ambitious, and self-conscious forms of creative literature. In the works of poets such as Dante, Petrarch and Chaucer new models of authorship and poetic identity were being explored, new kinds of philosophical and aesthetic value attributed to literary discourse. But these creative developments also brought with them new dangers and tensions, a sense of guilt and uncertainty about the value of creative literature, especially in relation to the dominant religious values of late medieval culture. In this thesis I explore how these doubts and tensions find expression in Chaucer's poetry, not only as a negative, constraining influence, but also as something which contributes to the shape and meaning of poetry itself. I argue that as Chaucer develops his own expansive, questioning poetics in The House of Fame and The Canterbury Tales, he problematises the principle of allegory on which the legitimacy of literary discourse was primarily based in medieval culture and the final fragments of The Canterbury Tales see Chaucer struggling, increasingly, to reconcile the boldness and independence of his poetic vision with the demands of his faith. This struggle, which emerges most strongly and polemically in the final fragments, I argue, runs in subtle and creative forms throughout the whole of Chaucer's work. By seeing Chaucer in this light as a poet not of fixed, but of conflicted and vacillating intentions - a poet productively caught drawn between 'game' and 'earnest', radical ironies and Boethian truths - I attempt to account, in a holistic manner, for the major dichotomies that characterise both his work and its critical reception.