Blaise Pascal (1623-1662) was born in Clermont Ferrand, the town which Charlotte visits. He was a mathematician, physicist and religious philosopher.
He died before completing the Pensées, which he originally entitled Apologie de la Religion Chrétienne (Defense of the Christian Religion). The collection of notes includes the argument that we should live as if God exists, because there's little disadvantage if He doesn't and everything to gain if He does. This idea became known as Pascal's Wager: