The issues in this dissertation reside at the intersections of, and relationships between, topics concerning the meaning of generic generalizations, natural language modality, the nature and role of moral principles, and the place of supererogation in the overall structure of the normative domain. In 'Generics and Weak Necessity', I argue that generics-exception-granting generalizations such as 'Birds fly' and 'Tigers are striped'-involve a covert weak necessity modal at logical form. I argue that this improves our understanding of the variability and diversity of generics. This chapter also argues that we can account for variability concerning normative generics within a modal approach to generics. In 'The Genericity of Moral Principles', I provide evidence for the view that moral principles are generic generalizations, and, on the basis of this claim, argue that moral principles do not provide adequate support for reasoning about the moral statuses of particular cases. In 'Supererogation and the Structure of the Normative Domain', I investigate the diversity of the central normative modal notions and argue that we should distinguish between two senses of supererogation based different ways deontic modals are sensitive to background information.