There has been a persistent suggestion that Heidegger's work has major implications for theology, and in particular for 'fundamental theology' or that area of theological thought which is concerned with the nature of God, of creation and of being human. Heidegger has had an astonishing influence on not just one, but several movements in 20th century theology, having influenced Catholic and Protestant theologians alike. Despite having been taken up so widely, his place in Christian theology has rarely been analysed as a problem within itself, and where it has, the verdict so far has been largely negative. By analysing carefully Heidegger's critique of his own work I have been able to show that there are flaws in the conventional view of a fracture separating his earlier and later work. This is a provocative approach in existing scholarship because it challenges the basis on which Heidegger is being read in English and French, and to some extent in German, as well as the way in which his connection with theology has been either posited or repudiated. By indicating what Heidegger believed himself to be doing in his own work it has been possible to relocate him in ' relation to theology. This has important implications for some recent re-evaluations of medireval theology, and in particular the work of St. Thomas Aquinas. Reading Heidegger in this way would appear to place his work as far more centrally concerned with the western theological tradition than is more usually allowed. I have undertaken a survey of all the major works published in his lifetime, and also many of his lecture courses now available in the eighty-one volume Gesamtausgabe of his collected works. The conclusions I have drawn include an evaluation of the relevant English-speaking secondary literature. I have coupled this with reference to the attempts by French theologians, and Jean-Luc Marion in particular, to respond to Heid egger's work. � In consequence my thesis seeks to indicate (1) the particular problems concerning the 'tum' described earlier; (2) the points of unity between Heidegger's early and later work; (3) that Heidegger' s relationship and indebtedness to Nietzsche and his conception of Nihilism and the "death of God" have been ill-understood. In the light of these three issues, I have suggested (4) that Heidegger' s work can be understood as representing a critique of Christian appropriations of and engagements with philosophical ideas central to Western metaphysics, and (5) his later work in particular is philosophically rigorous and represents a considerable challenge to future theological endeavour.