In 1614 the shogunate prohibited Christianity amidst rumors of foreign plots to conquer Japan. But more than the fear of armed invasions, it was the ideological threat--or "spiritual conquest"--that the Edo shogunate feared the most. This book explores the encounter of Christianity and premodern Japan in the wider context of global and intellectual history. M. Antoni J. Ucerler examines how the Jesuit missionaries sought new ways to communicate their faith in an unfamiliar linguistic, cultural, and religious environment--and how they sought to "re-invent" Christianity in the context of samurai Japan. They developed an original "moral casuistry" or "cases of conscience" adapted to the specific dilemmas faced by Japanese Christians.