This chapter offers a survey of religious dissimulation in early modern England, where questions concerning its legitimacy were, owing to the unpredictable course of the English Reformation(s), arguably more pressing than anywhere else in Europe. While most Catholic and Protestant theological authorities condemned dissimulation in principle, the practice must have been widespread and was perceived, at least by those in power, as a political reality that could not simply be ignored. This chapter outlines both ecclesiological and political justifications for tolerating those who dissembled their faith and argues that their ambivalent status and the often unstable practices of policing such religious dissimulation should be considered a central aspect of early modern approaches to the problem of religious toleration. Religious dissimulation was a highly controversial practice, and toleration for inward dissent was never a given. Especially in times of political crisis, church and state authorities frequently resorted to aggressive measures to access the secret beliefs of religious dissenters, which belied the Queen’s alleged refusal to make windows into men’s hearts.