These nine essays, commissioned on the initiative of the Philosophy section of the British Academy, address fundamental questions about time in philosophy, physics, linguistics, and psychology. Are there facts about the future? Could we affect the past? In physics, general relativity and quantum theory give contradictory treatments of time. So in the current search for a theory of quantum gravity, which should give way: general relativity or quantum theory? In linguistics and psychology, how does our language represent time, and how do our minds keep track of it? Contributors include John Lucas, Michael Tooley, Gregory Currie, Roberto Torretti, Julian Barbour, Jeremy Butterfield, Chris Isham, Karel Kuchar, James Higginbotham, and Michel Treisman.