Book excerpt: Martin Heidegger is the 20th century theology philosopher with the greatest importance to theology. A cradle Catholic originally intended for the priesthood, Heidegger's studies in philosophy led him to turn first to Protestantism and then to an atheistic philosophical method. Nevertheless, his writings remained deeply indebted to theological themes and sources, and the question of the nature of his relationship with theology has been a subject of discussion ever since. This book offers theologians and philosophers alike a clear account of the directions and the potential of this debate. It explains Heidegger's key ideas, describes their development and analyses the role of theology in his major writings, including his lectures during the National Socialist era. It reviews the reception of Heidegger's thought both by theologians in his own day (particularly in Barth and his school as well as neo-Scholasticism) and more recently (particularly in French phenomenology), and concludes by offering directions for theology's possible future engagement with Heidegger's work.