This article argues that Pierre Bayle (1647–1706) is not merely a theorist of religious toleration but also a theorist of religious radicalization. By exploring how religious dissenters experienced religious conformity as a kind of mental and spiritual torture akin to conventional forms of corporeal punishment, I demonstrate that Bayle’s influential defense of toleration and liberty of conscience hinges on his account of the psychological mechanism of religious radicalization. Demands for religious conformity do not convince dissenters of their error but of their lack of zeal for their faith. Bayle’s plea for toleration, more broadly, urges us to reflect on the ways that we invite those who are different from us into dialogue or risk alienating them even further, an urgent concern today as extremist religious and nationalist views are on the rise across the globe.