This article examines the role of disputation in the conversion narrative of the clergyman and poet William Alabaster, written after he converted to Catholicism in the 1590s. Disputation, a mode of debate that had developed in the universities, is a preoccupation of the narrative, and is here used to place the work within the immediate history of religious disputation, and in the wider struggle over scholarship that accompanied post-Reformation religious controversy. The article asks why formal disputation was so important to religious writers and polemicists, drawing on Alabaster's perception of reason and its relationship to faith. It is asserted that the convert's eagerness for scholarly disputation arose from a fusion of religious with intellectual assurance: certainty in faith, and in the academic process. A comparison with examples taken from a long catalogue of works describing public, cross-confessional disputation is then used to enhance our understanding of Alabaster's influences; the building-blocks of his newfound religious identity. Taking Alabaster as its model, the article directs attention not only to the hitherto undervalued phenomenon of public or ‘professional’ religious disputation in post-Reformation England, but also to the role played by reason and scholarship in the thought and faith of Catholic—and Protestant—divines.