Bertrand Russell was one of the most revered and important philosophers of the twentieth century. His early contributions include his derivation of all mathematics from principles of logic, which, though later undermined by Kurt Godel, was still an important development. He also was instrumental in developing and popularizing modern formal logic and set theory. His less academic accomplishments include a widely read and highly readable history of philosophy and an introductory work on the major problems of philosophy. Along with his friend and colleague G.E. Moore, Russell was responsible for many of the early developments that would become Anglo-English analytic philosophy.