Quantum gravity seeks a unified theory in which quantum matter is dynamically related to generally relativistic spacetime. Although a continuing work in progress, research programmes in the field such as string theory, loop quantum gravity, and causal set theory make it clear that a successful theory of quantum gravity will raise important challenges to our conceptions of space, time, and matter-perhaps abolishing them altogether as fundamental entities. But just as important, there is goo...

One of the greatest challenges in fundamental physics is to reconcile quantum mechanics and general relativity in a theory of quantum gravity. A successful theory would have profound consequences for our understanding of space, time, and matter. This collection of essays written by eminent physicists and philosophers discusses these consequences and examines the most important conceptual questions among philosophers and physicists in their search for a quantum theory of gravity. Comprising...