The aim of the thesis is to seek a way out of the impasse to which Post-Modernism seems to lead theology. It begins by considering the most hopeful resolution of the problem of faith and reason offered in twentieth-century theology, viz. Tillich's reformulation, concluding that `post-metaphysical' thinking has shown how we must go beyond this. The second chapter points a way forward by comparing and contrastingTillich's and Habermas' interpretations of reason. Fully to appreciate what is being discussed demands the historical review of the discussion from Kant to contemporary thinkers which is provided by Chapter 3. This leads to the clarification of the problem as one of understanding how a reason claiming to be universal can be related to a faith tradition resting upon particular historical events. The central section of the thesis is a detailed exposition of Habermas, of the criticism his theories have evoked and an indication of the way in which Derridas thought can supply the useful correction which Habermas' work needs. Chapter 4 examines Habermas' theory of discourse ethics, noting the Kantian emphasis it reveals, and seeks to assess the contribution of his theories as a recognition of the importance of a communicative reason. Chapter 5 is a further examination of the criticisms made of Habermas - of his understanding of the Freudian idea of the unconscious in particular. Its conclusion is that Haberman' views need to be supplemented by Derrida's better grasp of the other of reason. Chapter 6 introduces Derrida's views of the unconscious in relation to the discussion about the nature of reason, touching upon his interpretations of Freud and considering the central theme of deconstruction. This is examined more fully in Chapter 7 when it is argued that Derrida aims not to undermine reason, but to examine it from `a step beyond reason'. Though philosophical in his intent he uses both negative theology and ethics as examples of the singularity of the encounter with the other. Chapter 8 pursues Derridas understanding of singularity through his interpretation of Kierkegaard's Fear and Trembling. The analysis shows how this emphasis on the singularity of the religious encounter cannot be explained without recourse to such arguments as Habermas' theories. In criticizing Caputo's interpretation of Derrida attention is called to the necessity of retaining the tension between the Saying and the Said. In Chapter 9 Derridas recent views on religion are examined, notably the idea that both faith and reason depend upon an `acquiescence to the testimony of the other', a pre-autonomous encounter that precedes both religion and rationality. It is suggested that religion is the formulation of mediated singularities. At this point Levinas is introduced into the argument and reason is viewed as receiving from the other beyond the possibility of the I: humans are described as essentially hospitable beings. The concluding chapter recapitulates the argument and suggests that presenting faith as reason's other can itself be deconstructed on the grounds that the universal and the particular are always co-implicated. These co-implications are uncovered in both Habermas' view of reason and Derridäs concern for singularity. Thus an alternative understanding of the relation between faith and reason as already in contact is suggested. However, this use of Derrida cannot ignore the fact that his thought resists theological appropriation and that Habermas cannot explain why people should be moral. A `post-metaphysical' approach will not solve the problem of faith and reason, but it does reveal the importance - and the necessity in some sense - of the indeterminacy philosophy provides for theology in a pluralistic situation.