This essay argues that the use of conscience as a justification for dissent has an even longer history than has often been assumed by intellectual historians of the Reformation. Through a close examination of the English Wycliffite Sermons (c.1380s–1390s) and the Testimony of William Thorpe (1407), it offers the first extended consideration of the use of the word “conscience” in Wycliffite texts, using this as the point of departure for an assessment of Lollard characterisations of human interiority more generally. Wycliffite writers repeatedly emphasise the opacity of the inner life and its consequent authority, a rhetorical tendency inherited and adapted from Wyclif’s own writings and other Latinate discourses. This not only provides Lollards with a helpful strategy in their attempts to avoid prosecution for heresy, but also provides the somewhat shaky ground upon which a number of their doctrinal convictions rest—especially those pertaining to oral confession and membership of the Church. Conscience also provides an obvious connection between religious dissent and political rebellion, which is why it must be central to any future account of Lollardy’s relationship to class struggle or sedition more generally conceived. When writers like Thorpe refer to the soul as invisible, or to God as their only judge, they invoke a fundamental, if unstable, aspect of Wycliffite belief: an incipient but dynamic account of the relationship between individual conscience, interiority, and authority that was to find even greater expression in figures such as Martin Luther, Jan Huss, and Henry VIII.