This thesis is comprised of four papers that explore the nature and practical implications of moral doubt. It starts from the observation that the appropriate way to understand and handle moral doubt will depend on the nature of our moral judgements themselves. The first and second papers take a cognitivist view of moral judgements and analyse moral doubt in terms of partial degrees of belief in moral propositions. The first, The Relevance of Belief: Subjective Norms Under Empirical and Moral Uncertainty, (...) argues that this form of moral uncertainty is relevant to our choices and that the norms most directly relevant to choice under moral uncertainty are the action-guiding subjective norms of instrumental rationality. The second, Preference and Commitment Under Moral Uncertainty, proposes a particular way of accommodating moral uncertainty within a decision theoretic model of rational choice, and shows that this has substantial advantages over existing alternatives. The third paper, Attitudinal Ambivalence: Moral Uncertainty for Non-cognitivists, provides an account of moral doubt that is consistent with non-cognitivism, by analysing the phenomenon in terms of ambivalence in one’s moral attitudes. The fourth and final paper, The Balance and Weight of Reasons, draws out some implications of ambivalence, by exploring the way in which the overall weight of reasons are reflected in the preferences of rational agents. (shrink)