Bertrand Arthur William Russell (18 May 1872 – 2 February 1970), 3rd Earl Russell, was a British philosopher, logician, mathematician, historian, and social critic. At various points in his life, Russell was a liberal, socialist, and pacifist, but he acknowledged that he was neither of these in the deepest sense. Although he spent most of his life in England, Russell was born in Wales and died at the age of 98.

Russell led the British “revolution against idealism” in the early 20th century. He is considered one of the founders of analytic philosophy, along with his predecessor Gottlob Frege and his student Ludwig Wittgenstein, and is considered one of the most important logicians of the 20th century. He co-authored Principia Mathematica, an attempt to explain mathematics by logic, with A. N. Whitehead. His philosophical essay On Denoting is considered a paradigm in philosophy. His work still has a visible influence on logic, mathematics, set theory, linguistics, and philosophy, particularly the philosophy of language, epistemology, and metaphysics.