His political activism began first when he was a student, then a fellow, and then a lecturer at Trinity College, Cambridge University. In 1916 he was dismissed from Trinity because of his support for unpopular views, such as socialism and pacifism. In 1918 he was sent to jail for his opposition to World War One and his "radical pacifism". In 1958 Russell founded the Campaign for Nuclear Disarmament and he was a life-long anti-nuclear advocate. In 1964 he helped organize the Who Killed Kennedy Committee which questioned the findings of the Warren Commission report on the John F. Kennedy assasination. With the existentialist philosopher, Jean-Paul Sartre, Russell formed the Vietnam War Crimes Tribunal, in 1967. This group took an active and critical stance against the U.S. military involvement in Southeast Asia.

In addition to his political activism, Russell one the 1950 Nobel Prize for Literature and made significant contributions to philosophy. He and his collaborator, Alfred North Whitehead, published Principia Mathematica (1910-1913) which is considered a major treatise on logic. His philosophical interests included epistemology and his intellectual development from "logical atomism" to "neutral monism" is discussed in detail in his intellectual autobiography, My Philosophical Development published in 1959.