This dissertation asks how poets find language for the experience of conviction in a period in which much of the traditional language for belief has weakened with the loss of a shared religious culture. In chapters on Gerard Manley Hopkins, Seamus Heaney, Thomas Hardy, William Butler Yeats, and A. R. Ammons, I argue that the twentieth century sees a crucial change in the representation of conviction, as poets look for ways to replace a pre-Romantic idiom of vision and visitation with a description of the feeling of knowing that feels more suitable for a secular context. For some poets, that older idiom becomes a rich metaphorical resource for describing the feeling of conviction. We all still speak of having had "a revelation" when we want to attest to the suddenness and power with which a new idea asserts itself in our consciousness; Seamus Heaney, the latest of the poets I consider, fills his poems with scenes of vision and visitation as a way of answering the same evocative impulse. But many modern poets, Heaney included, recognize an imperative to psychological realism that makes those borrowed metaphors begin to feel inadequate. Here I trace five poets' efforts to invent a more integral and flexible poetic language for the intensity of the mind in engagement with its ideas: from Gerard Manley Hopkins's desire to make the music of his poetry reflective of a subtle kinesthetics of faith, to Ammons's delicate voicing, in idiom, tempo, and cadence, of the changing intensity of his own creative absorption. I argue that having a language for the feeling of conviction—one that feels appropriate in a secular context—furthers these poets' efforts to represent the life of the mind more generally and to represent spiritual experience in its distinctively modern forms.