This essay outlines the theology of “modern-day” devotion, as it can be found in the works of the Carthusian monk Henry of Coesfeld (d. 1410). This theology consists of a classical Thomist framework, infused with ideas from Brabantine and Rhineland mysticism (e.g., Ruusbroec, Suso) and Carthusian spirituality, in which contempt for the world, purity of the heart, progression in the virtues, repentance and inner renewal, Eucharistic piety, meditation on Christ’s humanity and passion, “Christiformity,” and the imitation of Christ, play a central role. While pointing at the “present-day” moral decline in the religious orders and the church, Henry’s idea of devotion relates to personal reform, a process of becoming congruent with the “ancient” examples of Christ and the saints. His theology is not anti-mystical and anti-intellectual in nature, but at the same time it warns against the pitfalls of curiosity (curiositas) and the excesses of mysticism.