Blaise Pascal

Blaise Pascal was a prodigy: he built a working mechanical calculator in his teens to help his father with tax accounts, settled questions about vacuum and air pressure by experiment, and worked out the beginnings of probability theory in letters with Fermat.

On the night of 23 November 1654 something happened that he wrote down on a scrap of parchment — fire, and the God of Abraham, Isaac and Jacob, not the god of philosophers and scholars — and he sewed the scrap into the lining of his coat and moved it to each new coat for the rest of his life. A servant found it after he died. He spent his remaining years defending the Jansenists at Port-Royal in the Provincial Letters and collecting notes for a book arguing the Christian faith to skeptics.

He never finished it; the notes were published as Pensees eight years after his death, and they have outlived almost everything written to answer them. He died at thirty-nine.