The Barth-Brunner correspondence, containing 174 letters, offers a glimpse into the dynamic interactions of two of the twentieth century’s greatest theological minds. The letters betray the personalities of both men as they engage in intense and explicit theological discussion, debate, and criticism. The correspondence is rife with references to other theologians and theological positions, giving a telling account of how Barth and Brunner viewed themselves in relation to Christianity and philosophy, as well as their teachers, contemporaries, and students, ultimately offering a unique glimpse into the theology and the history of the Christian church in the twentieth century. Accordingly, the letters will clearly challenge some popular conceptions.