Socially and politically significant Muslim communities are posing a challenge to the public spheres of Western Europe: can public reason in a liberal democracy be so conceived as to accommodate the religious reasons of Muslims and other religiously motivated citizens? This question, often discussed from the perspective either of political philosophy or of particular religious traditions, is addressed here instead by drawing on the theory and practice of inter-religious dialogue. The dialogue movement known as ‘scriptural reasoning’ is analysed for its potential to provide a way of conceptualising the nature of reasoning in the public sphere. ‘Reasoning with texts’, it is argued, is a way of describing much of the reasoning that takes place within the public sphere and not just religious reasoning. This approach to understanding public reasoning is established through a combination of example and theory. A model of communicative hermeneutics as public reason based on an (inter)textual rationality is proposed. As well as providing space for textually based religious arguments, this (inter)textual imagination can be situated alongside and complement postmodern developments of Jürgen Habermas’s conception of the public sphere. Whilst this approach to reasoning in the public sphere initially appears very different from the classic statement of the idea of public reason in John Rawls’s political liberalism, it is shown to have significant continuity with Rawls’s theory when this is viewed through the lens of the Supreme Court as exemplar of public reason. This highest level of public reason involving legislation is also a form of reasoning with texts. But in order for religious and more popular levels of public discourse and deliberation to impact on the political and legislative processes, these too must be conceived as modes of reasoning having some continuity with higher levels of public reasoning. It is such continuity that this thesis seeks to theorise.