Bertrand Russell (1872-1970).

Russell was one of the founding influences in the development of analytical philosophy and was primarily concerned with the foundational logic behind mathematics.

As well as contributing to philosophical life, he was an active teacher and political campaigner, especially against nuclear weapons. A controversial figure. He ran as a suffragette member for parliament, was imprisoned during the first world war for stating that American soldiers would be used as strike breakers in England, just like they were at home. He was refused a teaching post in the 30's at New York Uni on the grounds that his works were `lecherous, libidinous, lustful, venerous, erotomaniac, aphrodisiac, irreverent, narrow-minded, untruthful and bereft of Moral fibre.' He was awarded the Nobel Prize for literature in 1950.

It's generally held that his best work was done in the first two decades of the century where he examined theories of description, truth and experience, and the logical under-pinning of mathematics (the use of set theory to teach math is a direct ancestor of Russell's work).

Bertrand Russell

.For our purposes, one of Russell's most interesting formulations was `Russell's Paradox'. That is, if there is a Set of all sets, then does it contain itself? Russell's proof that the answer changes over time - that the answer is both yes and no depending on how far through the logic you go - gives rise to the idea of an algorithm, or computational procedure, which Turing used as the basis of the Turing Machine. Algorithms are the basis of computer programming, and their reliance on an underlying argumentative logic makes them a `logic prosthetic', rather than a transcendental class of their own - no matter how hard we try...

Principles of Mathematics (1902)
Prnicipia Mathematica (1910-13)
Analysis of Mind (1921)
Analysis of Matter (1927)
History of Western Philosophy (1945)
Human Knowledge, it's scope and limits. (1948)