Karl Barth's work "Fides quaerens intellectum" from 1931 is fundamentally significant in two ways. Firstly, it is the crucial document of the discovery of the line of thought that was classically developed in the "Church Dogmatics." Barth referred to it as the only appropriate approach for theology. Secondly, it offers a groundbreaking analysis and interpretation of Anselm's argument for the existence of God in the "Proslogion," which cannot overlook any engagement with this famous precursor of the ontological proof of God's existence. Thus, this book also provides a key to understanding Barth's theological method and interpreting Anselm's argumentation.