William David MacAskill (born 24 March 1987 as William David Crouch) is a Scottish philosopher. He is an Associate Professor of Philosophy at the University of Oxford, a Senior Research Fellow at the Global Priorities Institute and the Director and Founder of the Forethought Foundation for Global Priorities Research. MacAskill is also the author of Doing Good Better and What We Owe the Future, and the co-founder of Giving What We Can, 80,000 Hours and the Centre for Effective Altruism.