Karl Barth is widely considered the greatest theologian of the Twentieth Century, exerting a major influence in almost every area of theological thought in both Reformation and Roman Catholic traditions. Ecclesial Mediation in Karl Barth deals with one of the most important and controversial themes in Barth's theology, the relation between divine and human action. John Yocum argues that Barth's late rejection of the concept of sacrament, explicated in the final volume of his Church Dogmatics, is not only at odds with his account of the nature and importance of sacraments presented earlier in the Church Dogmatics but subverts important elements of his theology as a whole especially the mediation of divine grace in preaching and the Bible. Bringing Barth into fruitful dialogue with Yves Congar, Yocum contends that the notion of sacrament is crucial to an account of the divine-human relation that respects the character of both agents.