My research examines one of the most visible manifestations of the growing religious diversity in contemporary London: public polemical debates between Muslims and Christians who compete for converts and aim to refute the claims of each other's religion. In streets and parks, on Speaker's Corner and university campuses, at The British Museum and the corner grocery store, Muslims and Christians in London passionately debate one another. Why do they constantly seek out these encounters? Are these public "arguments" demonstrations of religious tolerance or intolerance? Are they a dangerous sign of religious agitation that can lead to extremism, or a form of cultural exchange that, despite appearances, is part of the process of two religious communities learning to live side by side? Do they ultimately produce friction or mutual recognition? To answer these questions, this interdisciplinary project analyzes the context and content of these encounters, tracking the mediation and circulation of these performances in order to understand the communities that are constituted in and around these phenomena. Amidst increasing religious diversity and "public" religious visibility in contemporary London, and indeed all of Europe, my research will provide a framework for understanding polemical religious discourse as performative speech acts, and the social dimensions of their production and reception.