Blaise (blɛz). 1623–62, French philosopher, mathematician, and physicist. As a scientist, he made important contributions to hydraulics and the study of atmospheric pressure and, with Fermat, developed the theory of probability. His chief philosophical works are Lettres provinciales (1656–57), written in defence of Jansenism and against the Jesuits, and Pens ées (1670), fragments of a Christian apologia

the derived SI unit of pressure; the pressure exerted on an area of 1 square metre by a force of 1 newton; equivalent to 10 dynes per square centimetre or 1.45 × 10–4 pound per square inch