Blaise Pascal

Key ideas

With Pierre de Fermat, Pascal worked out in 1654 how to divide the stakes of an unfinished game of chance, laying the foundations of probability theory and the idea of expected value.

In the Pensées he applied this reasoning to religion in Pascal's wager. Reason cannot settle whether God exists, he argued, but you must act one way or the other. If the possible gain is infinite and the cost finite, even a small chance makes belief the better bet. The argument is the ancestor of modern puzzles about tiny probabilities and huge payoffs, most directly Pascal's mugging.

The Pensées are also a sustained meditation on the human condition: our smallness between the infinitely large and the infinitely small, our restlessness and our habit of distracting ourselves from the thought of death.

“The heart has its reasons, which reason does not know.”

Blaise Pascal, Pensées 277, trans. W. F. Trotter (1910)

Life, briefly

Pascal was a prodigy, educated at home by his father. As a teenager he wrote a treatise on conic sections, and at nineteen he built one of the first mechanical calculators to help his father with tax work. He also did important experiments on air pressure and the vacuum.

After an intense religious experience in 1654 he turned increasingly to theology. He suffered from poor health for most of his life and died at thirty-nine, leaving the Pensées as a collection of notes for an unfinished book.

Major works

• Pensées (posthumous, 1670)
• Provincial Letters (1656–57)
• Treatise on the Arithmetical Triangle

Further reading

• EncyclopediaStanford Encyclopedia of Philosophy: Blaise Pascal
• WikipediaBlaise Pascal