Are there such things as moral truths? How do we know what we should do? And does it matter? Constructivism states that moral truths are neither invented nor discovered, but rather are constructed by rational agents in order to solve practical problems. While constructivism has become the focus of many philosophical debates in normative ethics, meta-ethics and action theory, its importance is still to be fully appreciated. These new essays written by leading scholars define and assess this new approach in ethics, addressing such questions as the nature of constructivism, how constructivism improves our understanding of moral obligations, how it accounts for the development of normative practices, whether moral truths change over time, and many other topics. The volume will be valuable for advanced students and scholars of ethics and all who are interested in questions about the foundation of morality.