Blaise Pascal
/pasˈkɑːl/ /paskal
/ (1623–62), French mathematician, physicist, and religious philosopher. He founded the theory of probabilities and developed a forerunner of integral calculus, but is best known for deriving the principle that the pressure of a fluid at rest is transmitted equally in all directions. His Lettres Provinciales (1656-7) and Pensées (1670) argue for his Jansenist Christianity.