This book originated from a discussion between the author, Derek Parfit and Wlodek Rabinowicz, and further developed in correspondence and intense discussions with Wlodek Rabinowics and John Broome. The author disputes the recent trend in metaethics that focuses on reasons rather than norms. The reader is invited to take a new look at the traditional metaethical questions of moral semantics, ontology, and epistemology. The author mainly concerns himself with particular aspects of these problems: Which are the problems of morality? Are there many different moral questions, or, do they all, in the final analysis, reduce to one? The bold claim made in this book is that there is just one: What ought to be done? Moreover, there is just one source of normativity, just one kind of 'ought'-question, which lends itself to an objectively correct and authoritative answer.