Bertrand Russell (1872-1970) was a British philosopher, logician, mathematician, historian, and social critic, known for his profound contributions to analytic philosophy, logic, and the philosophy of mathematics. Russell co-authored "Principia Mathematica" with Alfred North Whitehead, a monumental work that aimed to establish a logical foundation for mathematics. He is also known for his work in epistemology, particularly his theory of descriptions, which helped shape the development of modern linguistic analysis. As a public intellectual, Russell was an advocate for social reform, nuclear disarmament, and human rights.