From BBC's "QI": Stephen Bertrand Russell, Lord Russell. Marvellous figure. They say that his breath was not good. In the biographies of Canes and his contemporaries he had very bad breath, but he was a remarkable man. He wrote Principia Mathematica, which was a book determined to reinvent maths. 'Cause set theory produced all kinds of paradoxes which seemed to suggest that nothing could be proved or complete or consistent in mathematics, which was a huge shock, and so he had to set out to prove mathematics worked from the very first principles-- Alan Was he very, very good at sudoku? Stephen Oddly enough, he was said not to be that good at mental arithmetic. So, in order to prove mathematics from the very beginning, you have to establish the first principle of arithmetic, and that piece of symbolic logic [on screen] was proving that one plus one equals two. David It's a bit late, the 20th century, to prove that. I'd say. We've got quite a lot riding by the 20th century on one plus one being two, you know. Quite a lot of engineering happening, quite a complex international economy... Stephen Yeah. David If you find out that it doesn't equal two, what do we do? Just burn everything, 'cause God knows, anything could fall on our heads; money-- you might as well eat it; forget civilisation. Stephen Well, there is a general thought that if what was considered to be the sound foundations on which all mathematics rested were proved to be rocky, that it may mean that some of the ultimate answers of the universe will never be answered. But it's rather splendid to think you would give so much effort into proving one plus one-- Ronni What an extraordinary achievement. You just have to bring up his halitosis! It comes to something when you think you've achieved that in life... David Imagine meeting him at a party, though. Alan Old Stinky Russell. Phew! David "I met this bloke at a party; he stank, and when I asked him what he did, he said he'd proved that one plus one equals two!" Stephen I know. But it's very important. It's a very important principle to understand is that you can be gossipy about someone's private hygiene and think they are one of the greatest and most towering intellectual heroes that you could ever worship at. The two don't rule each other out. David Similarly, you can say that someone has very nice breath who is an idiot.