Catholic and Lutheran thought are differently structured, embodying divergent conceptions of self and God. Roman/Lutheran ecumenism, culminating in the 1999 "Joint Declaration," attempts to reconcile incompatible systems based on different philosophical presuppositions. Drawing on a wealth of material, the author considers these structural questions within a historical context. Kierkegaard is shown, in a complex model, to hold together strengths which historically have been exemplified by the two traditions. This is an important work in systematic theology which considers questions quite fundamental to Western religion. It should interest theologians of all backgrounds and church historians.