Pascal's younger sister, Jacqueline, states in a letter dated 24 October 1656 that he suffered from an insurmountable laziness when it came to writing letters. Only some dramatic miracle, like that of the Holy Thorn (which his older sister, Gilberte, recounts in her biography of her brother), or some significant secular event, could fillip him into writing a letter. While we possess literally hundreds of letters by Pascal's great contemporary, Leibniz, we possess only fifteen by Pascal. Yet the letters are so revealing that if they were the only extant writings of Pascal's that came down to us we could reconstruct an illuminating biography.