The Barth-Brunner correspondence contains 174 letters, and offers a glimpse into the dynamic interactions of two of the 20th century’s greatest theologians. The letters reveal 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, providing a telling account of how Barth and Brunner viewed themselves in relation to Christianity and philosophy. Additional commentaries reveal their thoughts on their teachers, contemporaries, and students, and ultimately offer a unique glimpse into the theology and the history of the Christian church in the 20th century, as well as the characters of the two men. Accordingly, the letters will clearly challenge some popular conceptions.