In inter faith relations, the Trinity is often seen as an embarrassing or irrelevant problem. This study proposes a different approach, seeing Trinitarian thought as a resource for dialogue. Drawing on the suggestions of Paul Tillich and Raimundo Panikkar, the author identifies six key issues to be addressed in Trinitarian dialogue. These are traced in two historical examples: the encounters of patristic Christianity with Greek philosophical religion, and of medieval Christianity with Islam. The final chapter draws lessons from these experiences to suggest a reshaping of Christian dialogue with Hindus, Muslims and other people of faith.