Bertrand Russell (1872-1970) was a British philosopher and mathematician. He is one of the founders of analytic philosophy, and he did a lot of work in trying to derive mathematics from axiomatic foundations. His most notable work there is Principia Mathematica (1910), coauthored with Alfred North Whitehead. He also wrote A History of Western Philosophy.
He had views on sex and relationships and marriage that were rather radical for his time, notably expressed in Marriage and Morals (1929). In 1940, when the City College of New York offered him a position, some clergymen and a concerned parent got outraged by what he had advocated, and in the "Bertrand Russell case", they forced the college to cancel his appointment. However, he found employment elsewhere.
Bertrand Russell considered himself an agnostic at least part of the time,  though Russell's UK English definition of agnostic many years ago was similar to the modern American definition of Weak atheist. 
- The Theologian's Nightmare Frightening Science fiction by Bertrand Russell