Blaise Pascal--scientist, theologian, philosopher, and rhetorician--was born in Clermont, in Auvergne, on 19 June 1623. Few writers of the seventeenth century have been as subject to hagiographic treatment. Those texts, which range from direct testimony to family lore mediated by many generations, from his sister Gilberte Périer to vicomte François-René Chateaubriand, form the core of biographical information about Pascal, but they are frequently tendentious and inaccurate.

The most challenging task presented to Pascal's biographers has been the separation of historical fact and verisimilar biographical interpretation from hagiographic fiction, not a lack of information about his life. Blaise was the only son of Etienne Pascal, a magistrate who served as president of the Cour des Aides of Montferrand, and he had two sisters, Gilberte (born 1620) and Jacqueline (born 1626). Although the family maintained titles of lower nobility--Etienne Pascal sometimes referred to himself as chevalier (knight), but Blaise...