John Slotanus

For many years he worked to defend Roman Catholicism against its opponents through preaching and writing.

In this role he exercised the offices of censor of the faith and papal inquisitor throughout the Archdiocese of Cologne and the Rhine country.

In the discharge of these duties Slotanus came into conflict with the learned Justus Velsius, who in 1556, on account of teachings deemed heretical by the Church, was obliged to leave Cologne.

Among Slotanus's various works those most worthy of mention are: Disputationum adversus hæreticos liber unus (Cologne, 1558); De retinenda fide orthodoxa et catholica adversus hæreses et sectas (Cologne, 1560); and De barbaris nationibus convertendis ad Christum (Cologne, 1559).

In the last-named work Slotanus displays the ardent missionary zeal which fired the religious men of his time.