In a century that was over run by child prodigies and polymaths one of the most fascinating and frustrating representatives of both subsets in the 1600s was with out doubt Blaise Pascal, who was born on June 19^{th} 1623.

At the tender age of 16 Pascal, who was a mathematical autodidact, inspired by the projective geometry of Gerard Desargues wrote a short brilliant paper on hexagons inscribed in conic sections the result of which is still known as Pascal’s Theorem. At the age of nineteen he constructed a two species calculating machine known as the Pascaline to help his father, a tax collector, with his calculations. The machine was too expensive and was limited by the fact that it could only add and subtract (it also never really functioned properly) so it never really caught on, however as practical calculators emerged in the 19^{th} century they included many technical features first developed by Pascal.

He would go on the produce further significant works in mathematics most famously in the field of binomial coefficients, Pascal’s Triangle (actually discovered much earlier by the Chinese) that we all learnt about at school (didn’t we!), and together with Pierre Fermat (he of the famous theorem) in the then slowly emerging field of probability; Pascal having corresponded with Fermat about the correct division of the spoils in an interrupted game of chance.

In the field of physics Pascal is best known for his extension of Evangelista Torricelli’s experiments with barometers, which led to the discovery of vacuums an important nail in the coffin of Aristotelian physics that argued that vacuums could not exists. It also annoyed Descartes whose whole mechanical theory of physics relied on the denial of the possibility of a void. More than this Pascal’s air pressure experiments were part of the work that air had weight and was therefore susceptible to gravity, which explains why the atmosphere is not blown away by the movement of the earth, being held in place by gravity its carried along, an important step towards the acceptance of heliocentricity. Pascal also made important contributions to both hydrostatics and hydrodynamics, inventing the hydraulic press amongst other things. Think about Pascal next time you jack up the car (assuming you use a hydraulic jack) to change a tyre. Interestingly his supposed most famous contribution to the physics of fluids, Pascal’s Law, which states that pressure exerted anywhere in a confined fluid is transmitted equally in all directions throughout the fluid was actually discovered somewhat earlier by the Dutch physicist Simon Stevin.

In his mathematical and physical publications Pascal also made several interesting but inconclusive and even contradictory remarks on the philosophies of mathematics and science and there in some dispute under the experts as to whether he is to be considered a philosopher of these subjects or not.

In my introduction I described Pascal as frustrating, why? In 1651, only 29 years old, and long established as one of the leading mathematical scientists of Europe, Pascal, a neurotic and hypochondriac, underwent a religious conversion and became a Jansenist. Based on the writings of the Dutch theologian Cornelius Jansen (1585 – 1638) Jansenism was a movement within the Catholic Church, which adhered strictly to the teachings of Augustinus and in particular preaching a form of predestination dangerously close to Calvinism, which led to its condemnation as heretical. At first Pascal’s conversion had little effect on his scientific work but in 1654 he underwent a second conversion that led to him abandoning science completely as sinful. This viewpoint is to a certain extent in line with Augustinus’ teachings as he had said that scientific works bring honour to their author but were in end effect a waste of time and energy.

Interestingly Pascal returned to his mathematical work one time after this second conversion, plagued by toothache one night he suppressed the pain by working on a complex geometrical problem. Apparently in his distress mathematics could bring him the solace that his deep religious belief could not.

Pascal’s religious fervour deprived the world of his mathematical abilities but not of his astounding intellect. The main centre of Jansenism was the Port-Royal Cloister in Paris and it was from here that the Port-Royal Logic was issued, an important textbook in the history of logic. Originally published anonymously in 1662 it was attributed to the Jansenist theologians Antoine Arnauld and Pierre Nicole but it is now accepted that Pascal played a significant role in its conception. In France Pascal is most celebrated not as a mathematician but as an author of literature, his *Provincial** Letters* and his *Pensées* are both regarded as classics of French literature and although both are intrinsically religious even a deist like Voltaire called the *Letters* the best-written book that has yet appeared in France.

Having been a child prodigy, a scientific genius and a literary giant Pascal completed the requirements necessary to become a bona fide legend by dying tragically at the age of 39.

An atheist like Voltaire? Voltaire himself vigorously denied that he was an atheist; and most of the historians of the Enlightenment with whom I am familiar treat him as a deist, somebody who believes in God while rejecting most of the traditional doctrinal trimmings. Of course one could assume that Voltaire was just protecting himself socially, but it seems to me that his outlook differs systematically from other figures of his era who really were atheists—I myself tend to buy into Jonathan Israel’s typology that distinguishes the radical and essentially atheistic Enlightenment of Spinoza, Bayle, and Diderot, and Holbach from the moderate Enlightenment of the English deists, Montesquieu, and Voltaire.

Have you got a different slant on this issue? I’d be interested to hear more of your take on the matter.

You are of course right about Voltaire, I’m afraid I got carried away whilst writing. It was common to refer to Voltaire as an atheist but he is more probably to be considered a deist.

To your question on the Enlightenment I’m afraid I know too little about the 18th century to risk a judgement but I will say, rather provocatively, that I’m not really sure that there ever was an Enlightenment and I mean that fairly seriously. I’m still working on that, come back in a couple of years and I’ll tell you what I’ve decided!

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Just to further strengthen the point of this excellent article. Pascal’s work with calculating machines is remembered in the name of the Pascal programming language. Likewise his work on pressure is reflected in the SI unit for pressure: Pascal.

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