Focusing on the Christian side, the author applies Bernard Lonergan’s three-fold structure of progress, decline, and redemption to Christian-Muslim history. The author identifies moments of each vector in the wider history—Arab-Christian apologetics (progress), demonization of Islam (decline), nonviolent witnesses (redemption). The author then highlights a twentieth-century example of development-progress and redemption, namely the cumulative insights of Charles de Foucauld, Louis Massignon, and Christian de Chergé, which led to and built upon the Vatican II statements about Muslims-Islam.