The thesis examines the theoretical relationship between law and ethics. Its methodology is informed by both the existentialist tradition of ethical phenomenology and the natural law tradition in legal theory. The main claim of the thesis is that a phenomenological analysis of ethical experience, as suggested by the writings of existentialist authors such as Jean-Paul Sartre and Emmanuel Levinas, provides important support for the natural law tradition. This claim is developed and defended through detailed engagement with the natural law theory (...) of John Finnis. Specifically, I contend that Finnis’ account of moral reasoning as applying the principles of practical reasonableness to a context of self-evident, basic values gains significant support from a phenomenological theory of ethical experience. Finnis’ emphasis on the irreducible role of choice in moral deliberation also finds support in the existentialist tradition. However, I criticise some key aspects of Finnis’ theory, including his emphasis on the transcendental character of the basic values and his account of legal obligation. I begin by outlining some central features of the existentialist approach to philosophy. I advance an interpretation of existentialism as ethical phenomenology. I then discuss some possible methodological connections between the existentialist and natural law traditions. This discussion provides the methodological framework for the remainder of the thesis. The thesis develops and defends a substantially original theory of the relationships between law, ethics and politics. The exposition begins with an account of the relationship between law and community that draws upon the work of Finnis and G. W. F. Hegel. I then outline a phenomenological theory of ethical experience, drawing in particular on the writings of Sartre and Levinas. I employ this phenomenological account of ethics to develop a conception of moral reasoning as reflective, good faith engagement with pre-reflective social judgements of ethical significance. This view of ethical experience and moral reasoning is then used as the basis for an examination of the concept of law and its relationship to political discourse. I turn next to the notions of legal authority and obligation. I argue that law, in the focal sense of the term, presents a generic, peremptory obligation that is necessarily moral in character. In the course of the argument, I critically discuss the conceptions of legal authority proposed by Joseph Raz, Adolf Reinach, H. L. A. Hart, John Rawls, Finnis, Jacques Derrida and Hans Kelsen. This view of legal obligation entails there are fundamental moral conditions that positive rules must satisfy to qualify as law, in the focal sense. I explore the nature of the moral framework created by these conditions through a detailed analysis of the ethical foundations of political discourse. I argue that political discourse is founded upon an ontological apprehension of the nature of humans as free, ethical beings, which finds expression in a developed notion of political freedom. I suggest that the distinction between positive and negative forms of freedom advanced by Isaiah Berlin is best understood in terms of the different types of political claims invoked by those conceptions. I develop this theory by reference to the work of Charles Taylor, Gerald C. MacCallum, Wesley Newcomb Hohfeld, W. D. Ross, Robert Nozick and F. A. Hayek. I conclude by discussing the role of ethical experience in the interpretation of legal materials. I argue that ethical judgements play an irreducible role in constructing the natural interpretive context for judicial reasoning. I engage with the work of Hart, Lon L. Fuller, Martin Heidegger, Hans-Georg Gadamer, Ferdinand de Saussure and Ronald Dworkin, among others. In the final substantive chapter of the thesis, the potential for ethical judgements to play a constructive role in judicial action is illustrated through a detailed discussion of the doctrine of government neutrality. (shrink)