Blaise Pascal (1623–1662) was a French mathematician, physicist, inventor, philosopher, and religious thinker, one of the most influential scientists of the seventeenth century. He was born on June 19, 1623, in Clermont-Ferrand, France, the third of four children and the only son of Étienne Pascal, a wealthy judge and tax collector with a strong interest in mathematics. His mother died when he was only three years old.
In 1631, Pascal's father moved the family to Paris and undertook the education of his children himself. He decided that Blaise should not study mathematics until the age of fifteen. Nevertheless, the young Pascal secretly began exploring geometry on his own. At the age of twelve, he independently discovered that the sum of the angles of a triangle equals two right angles. Impressed by his son's talent, his father abandoned his original plan and introduced him to leading mathematicians of the time.
At the age of sixteen, Pascal wrote his first important mathematical work, the *Essay on Conics* (1640), based on earlier research into conic sections. The work contained what later became known as *Pascal's Theorem*, one of the fundamental results of projective geometry.
In December 1639, the family settled in Rouen, where Étienne Pascal had been appointed tax commissioner for Upper Normandy. While assisting his father in administrative work, Pascal became interested in mechanical calculation. Between 1642 and 1645 he designed and built the *Pascaline*, one of the world's first mechanical calculators. About fifty prototypes were produced, but the machine was too expensive to achieve commercial success.
Pascal also made important contributions to physics. Through experiments on fluids and atmospheric pressure, he helped establish the principles of hydrostatics. His work led to what is now known as *Pascal's Law*, which describes how pressure applied to a confined fluid is transmitted equally in all directions.
In 1654, Pascal published his famous study of the *Arithmetic Triangle*, now known as *Pascal's Triangle*. His investigations into probability, conducted in correspondence with the mathematician Pierre de Fermat, laid the foundations of modern probability theory and combinatorics.
Although he suffered from chronic health problems throughout much of his adult life, Pascal continued his scientific work until 1654. That year, following a profound religious experience known as the "Night of Fire," he devoted himself increasingly to theology and philosophy. He became associated with the Jansenist community of Port-Royal and began writing works defending Christianity.
His most famous philosophical and religious work, the *Pensées* (*Thoughts*), remained unfinished at the time of his death. In it he attempted to provide a rational defense of Christian belief and presented the famous argument known as *Pascal's Wager*.
Blaise Pascal died in Paris on August 19, 1662, at the age of thirty-nine. Medical historians generally believe that he suffered from severe gastrointestinal disease and neurological complications. Despite his short life, Pascal left a lasting legacy in mathematics, physics, philosophy, and theology. The SI unit of pressure, the pascal (Pa), is named in his honor.
