Emil Brunner's theology is divided into three periods: predialectical (1914-1920), dialectical (1921-1927), and eristic-dogmatic (1928-1960). Each period is characterized by a particular epistemological construct, describing the source and medium of religious knowledge. The epistemological construct determines the content of Brunner's theology during each respective period. This dissertation analyzes Brunner's epistemology and shows how it applies to his doctrine of the atonement. Brunner's pre-dialectical theology grants an active epistemological role to the human religious subject. Abelard's exemplarist soteriology, which also emphasizes human initiative, best fits the mold of such an epistemology. Brunner's dialectical epistemology places the initiative entirely on the side of God. To coincide with this new epistemology, Brunner adopts Anselm's Cur Deus Homo as a soteriological model. Brunner refines his epistemology during his final period, granting a role to both God and humanity. His soteriology moves toward the type described by Gustav Aulen in Christus Victor.