Bertrand Russell, (1872-1970), British philosopher, mathematician, and Nobel laureate, whose emphasis on logical analysis influenced the course of 20th-century philosophy.

Born in Trelleck, Wales, on May 18, 1872, Russell was educated at Trinity College, University of Cambridge. After graduation in 1894, he traveled in France, Germany, and the United States and was then made a fellow of Trinity College. From an early age he developed a strong sense of social consciousness; at the same time, he involved himself in the study of logical and mathematical questions, which he had made his special fields and on which he was called to lecture at many institutions throughout the world. He achieved prominence with his first major work, The Principles of Mathematics (1902), in which he attempted to remove mathematics from the realm of abstract philosophical notions and to give it a precise scientific framework.

Russell then collaborated for eight years with the British philosopher and mathematician Alfred North White head to produce the monumental work Principia Mathematica (3 volumes, 1910-1913). This work showed that mathematics could be stated in terms of the concepts of general logic, such as class and membership in a class. It became a masterpiece of rational thought. Russell and Whitehead proved that numbers can be defined as classes of a certain type, and in the process they developed logic concepts and a logic notation that established symbolic logic as an important specialization within the field of philosophy. In his next major work, The Problems of Philosophy (1912), Russell borrowed from the fields of sociology, psychology, physics, and mathematics to refute the tenets of idealism, the dominant philosophical school of the period, which held that all objects and experiences are the product of the intellect. Russell, a realist, believed that objects perceived by the senses have an inherent reality independent of the mind.

 Russell condemned both sides in World War I (1914-1918), and for his uncompromising stand he was fined, imprisoned, and deprived of his teaching post at Cambridge. In prison he wrote Introduction to Mathematical Philosophy (1919), combining the two areas of knowledge he regarded as inseparable. After the war he visited the Russian Soviet Federated Socialist Republic, and in his book Practice and Theory of Bolshevism (1920) he expressed his disappointment with the form of socialism practiced there. He felt that the methods used to achieve a Communist system were intolerable and that the results obtained were not worth the price paid.

Russell taught at Beijing University in China during 1921 and 1922. From 1928 to 1932, after he returned to England, he conducted the private, highly progressive Beacon Hill School for young children. From 1938 to 1944 he taught at various educational institutions in the United States. He was barred, however, from teaching at the College of the City of New York (now City College of the City University of New York) by the state supreme court because of his attacks on religion in such works as What I Believe (1925) and his advocacy of sexual freedom, expressed in Manners and Morals (1929).

Russell returned to England in 1944 and was reinstated as a fellow of Trinity College. Although he abandoned pacifism to support the Allied cause in World War II (1939-1945), he became an ardent and active opponent of nuclear weapons. In 1949 he was awarded the Order of Merit by King George VI. Russell received the 1950 Nobel Prize for Literature and was cited as "the champion of humanity and freedom of thought." He led a movement in the late 1950s advocating unilateral nuclear disarmament by Britain, and at the age of 89 he was imprisoned after an antinuclear demonstration. He died on February 2, 1970.

 In addition to his earlier work, Russell also made a major contribution to the development of logical positivism, a strong philosophical movement of the 1930s and 1940s. The major Austrian philosopher Ludwig Wittgenstein, at one time Russell's student at Cambridge, was strongly influenced by his original concept of logical atomism. In his search for the nature and limits of knowledge, Russell was a leader in the revival of the philosophy of empiricism in the larger field of epistemology. In Our Knowledge of the External World (1926) and Inquiry into Meaning and Truth (1962), he attempted to explain all factual knowledge as constructed out of immediate experiences. Among his other books are The ABC of Relativity (1925), Education and the Social Order (1932), A History of Western Philosophy (1945), The Impact of Science upon Society (1952), My Philosophical Development (1959), War Crimes in Vietnam (1967), and The Autobiography of Bertrand Russell (3 volumes, 1967-1969).