The British mathematician and philosopher Bertrand Russell (7 letters) was born in 1872 and is widely considered one of the most influential figures of the 20th century. He made significant contributions to logic, mathematics, philosophy, and social reform. He is best known for his work on the foundations of mathematics, which he developed in his book Principia Mathematica. He also wrote extensively on the philosophy of language, epistemology, and ethics. His work has had a lasting impact on the fields of philosophy, mathematics, and science.