Miikka Ruokanen reveals the powerfully Trinitarian and participatory nature of Martin Luther’s conception of divine grace in his magnum opus The Bondage of the Will. The study establishes a genuinely new understanding of Luther’s major treatise opening up its ecumenical potential. Luther’s debate with Erasmus signifies not only a disagreement concerning free will, but the dispute reveals two contrasting understandings of the very core idea of the Christian faith. For Erasmus, the relationship of the human being with God is based on the rationally and morally acceptable principles of fair play. For Luther, the human being is captivated by the overwhelming power of unfaith and transcendental evil, Satan; only the monergistic grace of the Triune God and the power of the Holy Spirit can liberate him/her.Ruokanen verifies the Trinitarian vision of salvation