Blaise Pascal was born on 19 June, 1623 in Clermont France. Clermont is located in central France and is surrounded by a chain of volcanoes. A picture of Clermont is shown in Figure 1.
France at this time was a major power in Europe and was a Catholic stronghold. France was in the process of rebuilding after several decades of war between French Catholics and Protestants.
Pascal's Father was Étienne and his mother was Antoinette. He had two sisters – Gilberte who was older and Jacqueline who was younger. Blaise became very sick when he was about two years old and nearly died. He suffered from ill health throughout his life. His mother died when he was about three years old and he was raised by his father. His father was a tax commissioner in Clermont. In addition to being a civil servant, Étienne was fluent in latin and greek and was an accomplished mathematician. In 1631 Étienne sold his government position in Clermont (a common practice in that day) and moved his family to Paris. He invested in government bonds to support his family.
Étienne had definite ideas on how to educate his children so they were home-schooled by him. He wanted them to be well grounded in languages, history, and philosophy before they took on more advanced subjects such as mathematics. He told Blaise that he couldn't study mathematics until he was 15 years old. However, Blaise was intrigued by geometry and secretly developed some of Euclid's theorems using his own terminology. When his father found out, he realized that his son was very gifted in this area and gave him a copy of Euclid's Elements to study.
Étienne was also a member of a small discussion group who were interested in the newly emerging field of natural philosophy (science). This group met in the quarters of a catholic priest Marin Mersenne, himself an accomplished mathematician. Members of this group included, Pierre de Fermat, Gilles Roberval, and Girard Desargues. They were also in correspondence with René Descartes, Christiaan Huygens, and Thomas Hobbes. The group discussed current topics in natural philosophy and mathematics including their own research. Blaise accompanied his father to the meetings when he was about 13 and began taking part in the discussions. The group could tell that this was a very gifted child.
In 1638 Cardinal Richelieu, the First Minister, entered France into the thirty years war. This was a power struggle between various catholic and protestant states. In order to help raise money for this war he defaulted on the government bonds. This was a financial disaster for Pascal's father Étienne. He joined with others in a protest rally. Cardinal Richelieu was enraged and jailed most of the protesters. Étienne escaped, but had to go into hiding. Jacqueline, Blaise's younger sister, was also a child prodigy in poetry and drama. She appeared in a performance before Cardinal Richelieu that moved him deeply. After the performance Jacqueline approached the Cardinal and begged him to forgive her father, and to allow him to return. The Cardinal not only forgave him, but offered him a high administrative position in Rouen. The family moved there with him.
Pascal's father faced a very difficult situation in Rouen. Cardinal Richelieu had imposed very high taxes to pay for the war and the people were angry. There were frequent riots. Étienne was a very capable and honest administrator and eventually gained the peoples trust. However, he was heavily burdened by the voluminous calculations involved in keeping up with the ever changing tax rates. Blaise would help his father with the calculations.
Blaise corresponded with the discussion group in Paris and was kept up-to-date on current events. Mersenne sent Blaise a copy of a book by Desargues on conic sections. Blaise was intrigued by the way Desargues used projections in this study. In 1642 Blaise sent Mersenne a copy of his first mathematical paper entitled Essai pour les coniques. In this paper Blaise derived a theorem on hexagons now known as Pascal's Theorem. This theorem states that if a hexagon (a six-sided polygon) is inscribed in a conic section (circle, ellipse, …) and the opposite sides are extended until they intersect, then the three points of intersection will lie on a line. This theorem is pictured in Figure 2.
Père Mersenne was overjoyed to see the first major result from this child prodigy. He passed the paper on to his many contacts throughout Europe. Pascal's theorem became an important result in the field of mathematics known as projective geometry.
Blaise was also able to help his father with the many tax calculations by inventing the first mechanical calculator known as the Pascaline. There is a picture of one in Figure 3.
The design and operation of the Pascaline will be discussed in the section on Pascal's contributions to Science and Engineering. Not only was the design of this device impressive, but it involved a great deal of engineering to bring it into production.
In 1642 Evangelista Torricelli performed an experiment that brought into question a long held belief in the scientific community. He took a glass tube that was closed at one end and filled it with mercury. He placed the tube inverted in a dish filled with mercury (see Figure 4).
The mercury level dropped leaving a column of mercury in the tube and an apparently empty space at the top of the tube. Torricelli claimed that the top space was actually a vacuum and that the pressure of the air on the mercury in the dish was balancing the weight of the mercury column. This caused quite a controversy since most scientists at this time were followers of Aristotle and believed that a vacuum was impossible. Aristotle had claimed that nature abhors a vacuum.
Blaise's father along with a friend duplicated the experiment in 1646. At first Blaise doubted that the empty space was in fact a vacuum, but on reading Torricelli's explanation he became convinced. Before long he would conduct some crucial experiments validating Torricelli's claim.
In the winter of 1646 Étienne slipped on the ice and broke his hip. Two local bonesetters stayed for a period of time with the Pascals and cared for Étienne. These young men were members of the Jansenist sect within the Catholic church. The Jansenists followed closely the teachings of Augustine and thus had many similarities with the reformed Calvinists. Through many conversations with the two young men the Pascal family converted to Jansenism. Blaise, in particular was very excited about his new-found faith. However, there was one of their teachings that Blaise had difficulty in accepting. They encouraged their members to abandon all earthly pursuits including science. Blaise felt that this would be a waste of the gifts God had given him. You can read more about Pascal's faith in the section The Faith of Blaise Pascal.
In 1656–1647, while his father was recovering from his injury, Blaise performed a number of public demonstrations of Torricelli's experiment with various liquids. In 1657 he returned to Paris accompanied by his sister Jacqueline. She cared for Blaise during his frequent illnesses. In Paris Blaise resumed his vacuum experiments. His latter experiments concentrated on Torricelli's explanation that it was air pressure applied to the mercury in the dish that was balancing the mercury column. His most famous experiment was the one carried out on the mountain Puy de Dome that illustrated that air pressure decreases with altitude and thus that the mercury column drops in height. You can read more about these experiments in the section Pascal's contributions to Science and Engineering. During this time Blaise met twice with René Descartes to discuss their differing views on the possibility of a vacuum.
In the spring of 1649, Due to civil unrest in Paris, Blaise along with his sister Jacqueline and father Étienne returned to Clermont and stayed with the family of Gilberte, Blaise's other sister. They returned to Paris in November 1650 as the riots had died down. Blaise's father Étienne died on September 24, 1651. For many years Jacqueline had wanted to become a nun at Port-Royal Abbey, a stronghold of Jansenism. However, Étienne had refused to let her go. After her father's death Jacqueline entered the Abbey. Blaise was now, for the first time, all alone. The next few years were a difficult time for him.
Blaise became friends with an aristocrat the duc de Roannez. They shared a common interest in the intellectual topics of the day and both had a desire for an authentic Christian spirituality. The duke introduced Blaise to a new circle of friends. One of these friends was the chevalier de Méré who posed two gambling problems to Blaise. These problems resulted in a series of letters between Blaise and Pierre de Fermat that formed the beginning of probability theory. You can read more about these problems in the sections Contributions to Mathematics and Appendix B: Analysis of Unfinished Game Problem.
On the 23rd of November 1654 Blaise had a profound spiritual experience that changed his life. Blaise had always approached God through his mind using reason. But on this night he experienced the presence of God in a way that changed his heart. He never told anyone about this, but he wrote an account of this experience on a piece of paper and sewed it into the lining of his coat. The paper was discovered after his death when they were going through his clothes. This night is often referred to as his “Night of Fire” because of the references to fire in his account. There are more details in the section The Faith of Blaise Pascal. There were several stories that were later told about his “Night of Fire.” One story claimed that he had nearly died in a carriage accident which caused him to reassess his life. Another story claimed that he had been deeply moved by a sermon. No one really knows what happened that night except for what he had written Although he never told anyone about this spiritual experience, his friends could see a difference in his life. His anxiety and confusion were replaced by a calmness and a peace. He later told Jacqueline that he was now ready to completely embrace Jansenism. However, he still continued to work in mathematics and science and remained friends with the duke and his entourage. His continuation of these ‘worldly’ pursuits caused many of the Jansenists to question his commitment.
The Jansenists were continually under attack in the Catholic church, primarily by the Jesuits. These attacks were now increasing in intensity. A committee appointed by the Pope and the faculty of the Sorbonne condemned five of the core Jansenist beliefs as heretical. Antoine Arnauld, the current leader of the Jansenists, tried to defend their position, but was having little success. In desperation they turned to Pascal who penned the Provincial Letters. There were 18 letters in this collection written over a two year period 1656–1657. Pascal didn't use theological arguments, but instead used comedy and sarcasm to mock the Jesuits and to engender sympathy for the Jansenists. The Provincial Letters were very popular and widely read. It is said that Voltaire, an opponent of Christianity, carried a copy with him and kept one at his bedside to serve as a reminder of what good writing looks like. You can read more about these letters in the section Contributions to Literature.
Pascal's health continued to worsen in 1658. As a distraction he worked on the famous mathematical curve the cycloid. He was able, among other things, to find the area and center-of-gravity of this curve. Pacal's contributions can be found in the section Contributions to Mathematics. Pascal also announced his plans to publish a defense of Christianity. He didn't believe that the common man could follow the usual theological arguments. Instead he wanted to present arguments in the language of the people. He was never able to finish this work, but his notes were collected and published after his death as the Pensées. There is more on the Pensées in the section Contributions to Literature
Jacqueline Pascal died in October of 1661 shortly after being forced to sign a document drafted by the king condemning Jansenist beliefs. In 1662 Blaise instituted the first omnibus service in Paris. You can read more about this achievement in the section Contributions to Science and Engineering. Later that year he became seriously ill and died on August 19, 1662. He was buried inside the church Saint-Étienne-du-Mont and the family placed a small plaque on the wall near his tomb. A picture of the church where he is buried is shown in Figure 5 below.