**Blaise Pascal** (19 June 1623 – 19 August 1662) was a French **mathematician, ****physicist****, inventor, writer** and Christian **philosopher**. **He was a ****child prodigy**** who was educated by his father, a tax collector in ****Rouen****. Pascal’s earliest work was in the natural and applied sciences where he made important contributions to the study of ****fluids****, and clarified the concepts of ****pressure ****and ****vacuum**** by generalizing the work of ****Evangelista Torricelli****. Pascal also wrote in defense of the ****scientific method****.**

**In 1642, while still a teenager, he started some pioneering work on calculating machines. After three years of effort and fifty prototypes, he was one of the first two inventors of the ****mechanical calculator****. He built 20 of these machines (called ****Pascal’s calculators**** and later Pascalines) in the following ten years. Pascal was an important mathematician, helping create two major new areas of research: he wrote a significant treatise on the subject of ****projective geometry**** at the age of 16, and later corresponded with ****Pierre de Fermat**** on ****probability theory****, strongly influencing the development of modern economics and ****social science****. **

**Following ****Galileo**** and Torricelli, in 1646 he refuted ****Aristotle****‘s followers who insisted that ****nature abhors a vacuum****. Pascal’s results caused many disputes before being accepted. In 1646, he and his sister Jacqueline identified with the religious movement within ****Catholicism**** known by its detractors as ****Jansenism****. His father died in 1651. Following a religious experience in late 1654, he began writing influential works on philosophy and theology. His two most famous works date from this period: the ****Lettres provinciales**** and the ****Pensées****, the former set in the conflict between Jansenists and ****Jesuits****. **

**In that year, he also wrote an important treatise on the arithmetical triangle. Between 1658 and 1659 he wrote on the ****cycloid**** and its use in calculating the volume of solids. Pascal had poor health, especially after his 18th year, and his death came just two months after his 39th birthday.**

**Born in ****Clermont-Ferrand****; he lost his mother, Antoinette Begon, at the age of three. His father, ****Étienne Pascal****, who also had an interest in science and mathematics, was a local judge and member of the “****Noblesse de Robe****“. Pascal had two sisters, the younger ****Jacqueline**** and the elder Gilberte. ****Étienne, who never remarried, decided that he alone would educate his children, for they all showed extraordinary intellectual ability, particularly his son Blaise. The young Pascal showed an amazing aptitude for mathematics and science.**

**Particularly of interest to Pascal was a work of ****Desargues**** on ****conic sections****. Following Desargues’ thinking, the 16-year-old Pascal produced, as a means of proof, a short treatise on what was called the “Mystic Hexagram”, ***Essai pour les coniques*** (“Essay on Conics”) and sent it—his first serious work of mathematics—to ****Père Mersenne**** in Paris; it is known still today as ****Pascal’s theorem****. It states that if a hexagon is inscribed in a circle (or conic) then the three intersection points of opposite sides lie on a line (called the Pascal line).**

**Pascal’s work was so precocious that Descartes was convinced that Pascal’s father had written it. When assured by Mersenne that it was, indeed, the product of the son not the father, Descartes dismissed it with a sniff: “I do not find it strange that he has offered demonstrations about conics more appropriate than those of the ancients,” adding, “but other matters related to this subject can be proposed that would scarcely occur to a 16-year-old child.”**

**In 1642, in an effort to ease his father’s endless, exhausting calculations, and recalculations, of taxes owed and paid (into which work the young Pascal had been recruited), Pascal, not yet 19, constructed a mechanical calculator capable of addition and subtraction, called ****Pascal’s calculator**** or the Pascaline. Of the eight Pascalines known to have survived, four are held by the ****Musée des Arts et Métiers**** in Paris and one more by the ****Zwinger museum**** in ****Dresden****, Germany, exhibit two of his original mechanical calculators.**

**Though these machines are pioneering forerunners to a further 400 years of development of mechanical methods of calculation, and in a sense to the later field of ****computer engineering****, the calculator failed to be a great commercial success. Partly because it was still quite cumbersome to use in practice, but probably primarily because it was extraordinarily expensive the ****Pascaline**** became little more than a toy, and ****status symbol****, for the very rich both in France and elsewhere in Europe. Pascal continued to make improvements to his design through the next decade and he refers to some 50 machines that were built to his design.**

**Pascal continued to influence mathematics throughout his life. His ***Traité du triangle arithmétique*** (“Treatise on the Arithmetical Triangle”) of 1653 described a convenient tabular presentation for ****binomial coefficients****, now called ****Pascal’s triangle****. Pascal’s major contribution to the ****philosophy of mathematics**** came with his ***De l’Esprit géométrique*** (“Of the Geometrical Spirit”), originally written as a preface to a geometry textbook for one of the famous “****Petites-Ecoles de Port-Royal****” (“Little Schools of Port-Royal”)****. **

**The work was unpublished until over a century after his death. Pascal also used ***De l’Esprit géométrique*** to develop a theory of ****definition****. He distinguished between definitions which are conventional labels defined by the writer and definitions which are within the language and understood by everyone because they naturally designate their referent. The second type would be characteristic of the philosophy of ****essentialism****. **

**Pascal’s work in the fields of the study of ****hydrodynamics**** and ****hydrostatics**** centered on the principles of ****hydraulic fluids****. His inventions include the ****hydraulic press**** (using hydraulic pressure to multiply force) and the ****syringe****. He proved that hydrostatic pressure depends not on the weight of the fluid but on the elevation difference. In 1647, Pascal produced ***Experiences nouvelles touchant le vide*** (“New Experiments with the Vacuum”), which detailed basic rules describing to what degree various liquids could be supported by air pressure. It also provided reasons why it was indeed a vacuum above the column of liquid in a barometer tube.**