Blaise Pascal

Pascal was a prodigy who worked out much of elementary geometry alone as a boy and, at nineteen, built a mechanical calculator to spare his father the drudgery of tax arithmetic. With Fermat he laid the foundations of probability while answering a gambler's question about how to divide the stakes of an unfinished game. He demonstrated that air has weight by having a barometer carried up a mountain in the Auvergne and watching the mercury fall, and in the last year of his life he organised the first scheduled public transport in Paris, five-sou carriages running fixed routes.

After a night in 1654 that he recorded on a scrap of parchment sewn into his coat and found only after his death, he turned to religion and to the Jansenists of Port-Royal. The Provincial Letters savaged the moral reasoning of the Jesuits in French so clear that it changed how French prose was written. The Pensées, unfinished notes for a defence of Christianity, contain the wager and the observation that all human unhappiness comes from being unable to sit quietly in a room. He was ill most of his life and died at thirty-nine; he is buried in Saint-Étienne-du-Mont, behind the choir.