Albert Einstein was a German theoretical physicist noted for his theory of relativity. He won the Noble Prize for physics in 1921. Einstein was awarded Time magazine's person of the century award. He is by far the greatest physicist producing theories that have changed the way we look at the world. This volume contains Ether and the Theory of Relativity, which was as address delivered on May 5, 1920 at the University of Leyden. Also included in this volume is Geometry and Experience, which was an expanded form of an Address to the Prussian Academy of Sciences in Berlin on January 27th, 1921.