One of the persistent concerns in the wake of the forced conversion of Spanish Jews to Christianity was the precise nature of their religiosity. Forcibly baptized between 1391 and the second decade of the fifteenth century, the newly converted as well as their descendants were believed to be only nominally Christians. They were reported to be secretly practicing Jewish rituals, mocking Christianity, and even dissimulating Catholic worship while inwardly intending to Judaize. This essay explores how the Inquisition established the heresy of Judaizing, with a particular attention to the ways in which inquisitors understood the relations between exterior acts and intentionality. It argues that the desire to secure conviction prompted inquisitors to coerce the accused to confess their heretical inner intentions. This produced another forced conversion, this time in the sense of the return of fallen baptized Christians to the fold of the Church. It also shaped the historical records we have on New Christian religiosity, and therefore calls for a reconsideration of how historians should approach it.