The Reformation movements divided Christian Europe into competing and often warring denominational factions. Defining one's religious affiliation therefore became even more important a task than during the era of the medieval inquisition. In the pre-Reformation era, Catholic preachers and inquisitors had spread anxiety about heretics and blasphemers drawing down divine retribution in plagues or catastrophes, while inquisitions and judicial action proved fairly effective in suppressing most heretical movements across Europe by 1500. However, not all dissidents had given up their unorthodox beliefs; in many cases they had learned only to be very cautious in expressing them publicly, some following the example of Nicodemus, the disciple of Jesus who kept his affiliation secret.

Concealment of heterodox beliefs had also been suspected of the Lower Rhine mystics and especially of the supposed members of the ‘Brethren of the Free Spirit’, which was hardly the organized sect that inquisitors portrayed it to be. The mystical tendency to internalize spirituality was taken by the orthodox to imply depreciation, even renunciation, of external religious forms, and at times there was some truth to this suspicion. Such misgiving quickly became attached to the famed Dutch humanist Erasmus of Rotterdam (1466–1536), who satirized popular devotion to saints, relics and sacramentals. The late medieval Devotio Moderna's emphasis on the inner reception of the sacraments was seen by many churchmen as potentially anticlerical.