Bertrand Arthur William Russell, 3rd Earl Russell, OM, FRS (18 May 1872–2 February 1970), was a philosopher, historian, logician, mathematician, advocate for social reform, and pacifist. Although usually regarded as English, he was born in Wales. A prolific writer, he was a populariser of philosophy and a commentator on a large variety of topics. Continuing a family tradition in political affairs; he was a prominent anti-war activist, championing free trade between nations and anti-imperialism. He also authored Principia Mathematica (with Alfred North Whitehead), an attempt to ground Mathematics on the laws of Logic and the essay On Denoting. Both books have had a considerable influence on Logic, Set Theory, Linguistics and Analytic Philosophy. Bertrand Russell was born at the height of Britain's economic and political ascendancy.
When he died almost a century later, the British Empire had all but vanished, its power had been dissipated by two world wars and its imperial system had been brought to an end. Among his post–Second World War political activities, Russell was a vigorous proponent of nuclear disarmament, antagonist to communist totalitarianism and an outspoken critic of the Vietnam War.