Bertrand "Bertie" Russell (May 18, 1872 – Feb. 2, 1970) was a British mathematician, pacifist, socialist (no, really), philosopher and logician. He also wrote books and essays for popular audiences; a good many of these were full of his signature snark about religion. Russell's Teapot is a good example of this.
Along with Gottlob Frege and Ludwig Wittgenstein, he's considered one of the founders of Modern Analytic Philosophy, and one of the greatest logicians of the 20th century.
He coauthored Principia Mathematica with A. N. Whitehead, which attempted to use symbolic logic to derive mathematics from basic axioms. (1+1=2 is proved in Volume II.) It is highly regarded by many mathematicians, but is pretty unreadable unless you have a brain the size of a planet, or no life. The book was an attempt to make Hilbert's Program a reality by its use of a finite and small set of axioms with which one could (in principle) derive all of modern mathematics. PM is essentially an attempt to make all of mathematics constructive. Austrian logician Kurt Gödel eventually proved that PM is incomplete, which means that it does not have the ability to produce theorems that prove everything within its particular domain (all of mathematics in this case). The reason for this was essentially that Russell and Whitehead overlooked meta-mathematics, and did not believe (or it did not ever occur to them) that their system could be used to reason about meta-mathematical concepts. Gödel observed that you could in fact use PM with meta-mathematics, and he promptly invented Gödel-numbering, which allows one to prove things about PM itself in PM. Contrary to popular belief, he did not prove that it was "wrong", "inconsistent", "useless", or any other adjective that implies incorrect.
 Well known publications
- History of Western Philosophy (1946)
- Why I Am Not a Christian (1929)