This book will be of interest to physicists and historians of science. Paul Adrien Maurice Dirac was one of the founders of quantum theory. He is numbered alongside Newton, Maxwell and Einstein as one of the greatest physicists of all time. Together the lectures in this volume, presented on the occasion of the dedication ceremony for a plaque commemorating Dirac in Westminster Abbey, give a unique insight into the relationship between Dirac's character and his scientific achievements. Four lectures given by internationally respected physicists, Abraham Pais, Maurice Jacob, David Olive and Sir Michael Atiyah follow the text of the dedication address given by Stephen Hawking.