Blaise Pascal (1623-1662), French mathematician, physicist, inventor, philosopher, writer and Catholic theologian. At 19, Pascal invented a mechanical calculating machine based on cogs, also known as a pascaline (calculator). Pascal also made contributions to geometry and hydrostatics. He worked with French mathematician Fermat, founding probability theory. The SI unit of pressure, the Pascal, was named after him to honour his work on hydrostatics. Copperplate engraving from the Encyclopaedia Londinensis, or Universal Dictionary of Arts, Sciences, and Literature; Volume XVIII; Edited by Wilkes, John. Published in 1821.