Philosopher Derek Parfit claimed that nothing matters unless ethical and other normative beliefs are objectively true. Parfit, who died on 1 January 2017, wrote a three-volume work, On What Matters (2011–17), because he believed that the meaningfulness of his life, and the lives of others who devote themselves to ethical thought, depend on demonstrating the reality of normative properties and the necessity of basic ethical truths. This collection of essays, edited by Peter Singer, is a response by some moral philosophers to Parfit’s views about ethics, normativity, and meaning.

Parfit, though scarcely known outside the world of philosophy, was one of the most important thinkers of the late twentieth and early twenty-first centuries. His earlier work, Reasons and Persons (1984), made an impact mostly because of its claims about personal identity and duties to the unborn. He turned to the esoteric field of meta-ethics, the study of the meaning of ethical propositions, and the foundation of our ethical beliefs, because he became convinced that the very possibility of ethical truth depends on defeating David Hume’s view that values depend on our desires.