Actions that go 'beyond the call of duty' are a common though not commonplace part of everyday life - in heroism, self-sacrifice, mercy, volunteering, or simply in small deeds of generosity and consideration. Almost universally they enjoy a high and often unique esteem and significance, and are regarded as, somehow, peculiarly good. Yet it is not easy to explain how - for if duty exhausts the moral life there is no scope to praise supererogatory acts, and if the consequentialist is right there are no grounds for awarding them a special status. However, despite the distinctiveness of supererogation and the difficulty of accounting for it, philosophers have paid surprisingly little attention to the concept, and until now no thorough and systematic treatment of it has been proposed. This is what David Heyd offers in this book. His study will stimulate philosophers to recognise the importance of this rather neglected topic, and to take a fresh critical look at their theories in the light of its singular importance.