While the Welsh poet Dylan Thomas (1914-1953) gained fame and notoriety as the epitome of unbridled poetic genius and bohemian excess, his writings remained relatively neglected by the academic mainstream for a long time: too obscure was his work, too dominant in his readers' minds were the rumours and legends surrounding his life and death. A systematic study of Thomas's Collected Poems does however reveal that the much criticised obscurity of his work is simply a result of his consistent attempts at stacking meaning upon meaning in his poems in order to fashion a unified vision in a time of fragmenting world views and global crises. The present study seeks to place Thomas’s writing into the wider context of European literature, tracing diverse uses of ambiguity through antiquity, the middle ages and early modern times. Central considerations and concerns of the twentieth and twenty-first centuries with regard to this stylistic device are then discussed in order to arrive at a taxonomy of poetic ambiguity. After reading Thomas’s oeuvre against this matrix, the present study places particular emphasis on two aspects that play a pivotal role in Thomas’s use of ambiguity – the religious or quasi-religious nature of his writing and his (rarely acknowledged) participation in literary modernism.