In late 1644, the Minim friar Marin Mersenne (1588-1648) travelled to Florence and assisted Evangelista Torricelli (1608-1647) in repeating his famous barometric experiment. When Mersenne returned to France, he shared Torricelli’s discovery with his network of correspondents, “giving rise to flourishing experimental and theoretical activities,”¹ including the famous work on the weight of air conducted by Blaise Pascal (1623-1662). This is one of many contributions Mersenne would make to the scientific enterprise.

Called “an architect of the European scientific community”² and “one of the most important figures in the history of modern thought,”³ Mersenne is virtually unknown to non-historians, although mathematicians may recognize his name from Mersenne Primes.⁴

Mersenne was one of the greatest facilitators and correspondents in the history of science, acting as a “clearing house for scientific and philosophical information in the decades just prior to the appearance of the first learned journals.”⁵ In 1635, Mersenne created the Académie Parisienne, a precursor to the Académie des Sciences.

One of Mersenne’s closest collaborators was Rene Descartes (1596-1650). Both men had attended the Jesuit College at La Flèche, although Descartes was several years younger. Later, Mersenne would assist in the publication of Descartes’ Discourse on Method, and, after Descartes relocated to the Dutch Republic, Mersenne would keep the Father of Modern Philosophy updated on French intellectual developments, while acting as “Descartes’ mouthpiece to the republic of letters.”⁶ Furthermore, it was in Mersenne’s quarters that Pascal met Descartes,⁷ a meeting of the minds in the truest sense.

In addition to Torricelli, Pascal, and Descartes, Mersenne’s friends and correspondents included the mathematicians Pierre de Fermat⁸ and Girard Desargues,⁹ philosopher Thomas Hobbes,¹⁰ and the churchman-astronomer Nicolas-Claude Fabri de Peiresc.¹¹ In total, Mersenne corresponded with 140 key thinkers from throughout Europe (and as far away as Tunisia, Syria, and Constantinople),¹² and his compiled correspondence now fills 12 volumes.

Mersenne, however, offers us much more. He made several other important contributions to the scientific enterprise, especially in the fields of acoustics, scientific methodology, telescope and pendulum theory, and in the study of the motion of falling objects.

Mersenne is often credited as one of the founders of acoustics. In this field, he pioneered “the scientific study of the upper and lower limits of audible frequencies, of harmonics, and of the measurement of the speed of sound,¹³ which he showed to be independent of pitch and loudness.” Furthermore, he “established that the intensity of sound, like that of light, is inversely proportional to the distance from its source.”¹⁴ His work in acoustics is immortalized in his eponymous three laws describing the relationship between frequency and the tension, weight, and length of strings.

As one of the most influential proponents of the mechanistic philosophy of nature,¹⁵ Mersenne’s contributions to scientific methodology are also significant. Mersenne, who was inspired by Francis Bacon,¹⁶ was an ardent defender of the rationality of nature, as well a strong opponent of magic and the occult.

His “insistence on the careful specification of experimental procedures, repetition of experiments, publication of the numerical results of actual measurements as distinct from those calculated from theory, and recognition of approximations marked a notable step in the organization of experimental science in the seventeenth century.”¹⁷ The Catholic Encyclopedia (a sympathetic voice, to be sure) goes as far as identifying the work of Mersenne and Galileo in experimenting with the weight of air as “the beginning of the development of the experimental method”¹⁸ (This experimentation was not his only connection to the great Italian scientist: Mersenne translated Galileo’s work on mechanics¹⁹ and helped to spread Galileo’s ideas in France).

In his work with pendulums, Mersenne discovered that “the frequency of a pendulum is inversely proportional to the square root of its length.”²⁰ He also discovered the length of a seconds pendulum, and (against Galileo) that pendulum swings are not isochronous. Furthermore, Mersenne’s suggestion to Christiaan Huygens (1629-1695) that the pendulum could be used as a timing device partially inspired the pendulum clock.²¹

Mersenne did much more than contribute significantly to the scientific enterprise. He engaged and embraced the best ideas and minds of his time. In his century of genius, the power of the human mind reached new heights in its ability to understand the laws of nature. Against this backdrop, Mersenne championed the unity of truth.²²

Encouraged by his order and always a loyal son of the Church,²³ Mersenne was operating at the heart of the Scientific Revolution. And he demands the attention today of both Catholics and atheists.
 
 
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Herbert Butterfield, the influential twentieth-century historian, identified the Scientific Revolution as “one of the great episodes in human history,” which, along with the rise of the empires of Alexander the Great and ancient Rome, deserves a place “amongst the epic adventures that have helped to make the human race what it is.”¹ Numerous Catholic scientists, both laymen and churchmen alike, made valuable contributions to science before, during, and after the Scientific Revolution.

The scientists and mathematicians of the Jesuit Order hold a special place in this story, and a multi-volume work would be required to catalogue their contributions to a variety of scientific fields. In this article, we examine only one aspect of the Jesuit contribution, namely, their collaboration with the greatest minds of the Scientific Revolution.

Jesuit historian Joseph F. MacDonnell discusses the scientific influence of the Society of Jesus in his book Companions of Jesuits: A Tradition of Collaboration, where he writes that “it is a challenge for historians to find a single significant scientist of the sixteenth, seventeenth and eighteenth centuries who was not in some way involved with Jesuits and their colleagues: as students, as teachers, as relatives, as collaborators, as adversaries, as rivals or simply as personal friends.”²

The Jesuits had a close and often complex relationship with Galileo Galilei (1564-1642). While the Galileo Affair holds a prominent place in the history of science, the relationship between Galileo and the Church is more nuanced than often presented in standard histories. The same can be said of the relationship between the Jesuits and Galileo.

While the Jesuits often embraced Aristotelian science and the Tychonic model of the solar system, they still influenced Galileo in important ways. The historian William Wallace, for instance, has shown that many of Galileo’s views were inspired by several Jesuits teaching at the Roman College.³

After Galileo described his observations of the Moon and the Medicean Stars in his Starry Messenger of 1610, the Jesuits confirmed his discoveries. Furthermore, Galileo’s interest in the study of falling bodies originated with the Jesuit Niccolo Cabeo (1586-1650).⁴ Another Jesuit, Honore Fabri (1608-1688), was the first to explain Galileo’s experiment demonstrating equal time for falling bodies.⁵

Galileo’s lifelong friendship with the Jesuit astronomer and mathematician Christopher Clavius (1538-1612) began in 1587.⁶ Clavius, who introduced plus (+) and minus (-) signs to Italy,⁷ and is remembered for his work on the Gregorian calendar, was a great influence on the Father of Modern Science. In 1588, Galileo wrote a letter of admiration to Clavius, in which he also inquired about a center-of-gravity demonstration.⁸ A letter from Clavius brought Galileo enough joy to occasion an immediate recovery from a sickness that required Galileo to be bedridden.⁹

Another close collaborator with the Jesuit Order was Johannes Kepler (1571-1630), whose laws of planetary motion hold a special place in the history of scientific discovery. When Kepler found himself in financial difficulty and lacking a telescope of his own, the Jesuit mathematician Paul Guldin (1577-1643) encouraged fellow Jesuit Niccolo Zucchi (1586-1670) to provide Kepler with the needed instrument. Kepler, who was very appreciative of the gift, dedicated his last book to Guldin.¹⁰ The dedication reads:

“To the very reverend Father Paul Guldin, priest of the Society of Jesus, venerable and learned man, beloved patron. There is hardly anyone at this time with whom I would rather discuss matters of astronomy than with you. Even more of a pleasure to me, therefore, was the greeting from your reverence which was delivered to me by members of your order who are here. Fr. Zucchi could not have entrusted this most remarkable gift – I speak of the telescope – to anyone whose effort in his connection pleases me more than yours. Since you are the first to tell me that this jewel is to become my property, I think you should receive from me the first literary fruit of the joy that I gained from trial of this gift.”¹¹

This dedication from Kepler to Guldin came at the end of a long history of friendship with the Order. When Kepler was banished from the University of Graz, after a decree from the Emperor of Austria, the Jesuits Decker, Lang, and Guldin interceded on his behalf. The Jesuits at the college at Ingolstadt assumed responsibility for the publication of Kepler’s Almanac, after the scientist was unable to get it printed.¹²

The influence and encouragement flowed in both directions. For instance, Jesuit missionaries in China sought out his expertise on difficult mathematical problems, and Kepler encouraged the astronomical work of Zucchi.

The Jesuits also influenced Kepler’s fellow countrymen, Gottfried Leibniz (1646-1716) and Otto von Guericke (1602-1686). In a 1703 letter to Bernoulli, Leibniz attributed his original interest in mathematics to the writings of the Jesuits Clavius, St. Vincent, and Guldin.¹³ Indeed, Leibniz credits Gregory St. Vincent (1584-1667) as one of the founders of analytic geometry.¹⁴ After a meeting with Jesuit Chinese missionaries, Leibniz sent a suggestion for explaining the Trinity to their soon-to-be Chinese hosts.¹⁵

Guericke, who invented the air pump, was a friend and correspondent of the Jesuit Gaspar Schott (1608-1666). “It was Schott’s publication of von Guericke’s research,” writes Macdonnell, “that stimulated Huygens and Boyle as well as others to extend the experiments and thus to improve the vacuum pump.”¹⁶ Schott was also the first to make Boyle’s subsequent investigations of the air pump known in Germany.¹⁷

As suggested above, the Jesuits also greatly influenced members of the Huygens family. The Jesuit Francois d’Aguilon (1567-1617) composed a work entitled The Six Books of Optics, which not only influenced Christiaan Huygens (1629-1695), but also the mathematician Girard Desargues (1591-1661), who is credited as one of the founders of projective geometry.

The Six Books of Optics, which was illustrated by Peter Paul Rubens, was praised by Constantijn Huygens, Christiaan’s father. Constantijn, who thought The Six Books of Optics was the best book on geometrical optics he had ever read, compared d’Aguilon to Plato, Eudoxus, and Archimedes.¹⁸

The Jesuit influence was not limited to Continental scientists, but extended to important thinkers in England as well. The Jesuit Francesco Maria Grimaldi (1618-1663) discovered the diffraction of light and published his findings in 1665,¹⁹ and Isaac Newton became interested in optics as a result of Grimaldi’s work.

Newton first learned of the discoveries of Grimaldi through Fabri.²⁰ Robert Hooke (1635-1703) performed experiments with diffraction after reading of Grimaldi’s discoveries in the Philosophical Transactions of the Royal Society.²¹ Hooke also translated the first treatise on lighter-than-air flight, which was written by the Jesuit Francesco Lana de Terzi (1631-1687), and presented Terzi’s plan to the Royal Society.²²

The Englishman Robert Boyle (1627-1691) also appreciated the work of the Jesuits:

“Among the Jesuits you know that Clavius and divers others, have as prosperously addicted themselves to mathematics as divinity. And as to physics, not only Scheiner, Aquilonius, Kircher, Schottus, Zucchius and others, have very laudably cultivated the optical and some other parts of philosophy, and [also did] Ricciolus himself, the learned compiler of that voluminous and judicious work the Almagestum Novum.”²³

Similar histories could be written for Cassini, Fermat, Descartes, Harvey, and Torricelli. The influence of the Jesuits on the illustrious thinkers of the Scientific Revolution is only one chapter in the long story of their incredible contributions to science. These contributions are only now beginning to be fully appreciated by historians of science.
 
 
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In late December 1668, in a contest held at the Chinese Bureau of Astronomy, the Jesuit Ferdinand Verbiest (1623-1688) correctly predicted the length of a shadow cast by a vertical rod. The Kangxi Emperor was impressed. But he challenged Verbiest to two additional tests: the prediction of the exact position of the sun and planets on a given day and the timing of an approaching lunar eclipse. Verbiest successfully completed the final two tests, and, in the process, showed that the Chinese had much to learn from their Jesuit visitors.

With his scientific prowess firmly established, Verbiest became close with the Emperor, often accompanying him on excursions throughout the empire. Verbiest would make the most of this opportunity. Before he had passed on from this life, he had designed a self-propelled vehicle, cast cannons for the imperial army, written a 32-volume handbook on astronomy, composed a 2000-year table of future eclipses, and rebuilt the imperial observatory, enriching it with several bronze astronomical instruments. His funeral serves as an indication of his achievements: it featured musicians, standard bearers, and fifty horsemen.¹

Verbiest is one of many illustrious Jesuits to make valuable contributions to Chinese science. By 1800, more than 900 Jesuit missionaries had reached China.² It was science that served their primary purpose of sharing the Catholic faith and allowed the Jesuits to wield significant influence in China. Verbiest clearly understood the importance of science to evangelization efforts: “As a star of old brought the magi to the adoration of the true God, so the princes of the Far East through knowledge of the stars would be brought to recognize and adore the Lord of the stars.”³

The Jesuit Chinese missions represent one of the great untold stories of modern history. Jesuit missionaries would introduce the telescope and the discoveries of Galileo, determine the Russo-Chinese border,⁴ discover a land route between India and China,⁵ introduce European astronomy and mathematics, revise the Chinese calendar, map out the empire using modern methods, introduce stereographic projection of maps, participate in the division of China into time zones, and discover that Korea was a peninsula rather than an island.

Besides Verbiest, several other missionaries stand out for their valuable contributions. Matteo Ricci (1552-1610), a student of Jesuit mathematician and astronomer Christopher Clavius, inaugurated the Jesuit missions in China when he reached Macau in 1582. Eventually adopting the dress of Chinese scholars and acting as an adviser to the Imperial court, Ricci introduced Christianity and recent European scientific discoveries to his Chinese hosts. In mathematics, he was the first to introduce trigonometry⁶ and the works of Euclid⁷ to China.

Ricci’s most important scientific contribution, however, was his Impossible Black Tulip map, a cartographical wonder that greatly expanded Chinese geographical knowledge and was considered more accurate than contemporary maps of Europe.⁸ While previous Chinese world maps showed only the fifteen provinces of China surrounded by water and a few islands,⁹ the Impossible Black Tulip is the oldest surviving Chinese map to show the Americas. A 1602 edition of the map recently sold for $1 million and was displayed at the Library of Congress.

Ricci not only introduced European science to China, he was the first to provide Europe with an account of Chinese geography, culture, and literature. Ricci was more than a herald of scientific discoveries: he may one day be a saint. The Church has named Ricci a Servant of God, which denotes that his cause for beatification and canonization has been set in motion.

Another important Jesuit missionary is Adam Schall von Bell (1592-1666), an accomplished astronomer who entered Macau in 1619. By the time Schall von Bell reached China, the Chinese calendar, which had been used for 40 centuries, was in desperate need of revision. After arriving in Beijing in 1630, Schall von Bell began working tirelessly on calendar reform. Indeed, during his life, he would write no less than 150 treatises on this subject.¹⁰ In 1644, Schall von Bell was able to earn the respect of the Chinese government by correctly predicting an eclipse (The Chinese astronomers had erred by an hour in their prediction). After Schall von Bell’s astronomical feat, he was appointed director of the Board of Astronomy, the first Jesuit to fill this post.¹¹

With his newly earned position of authority, he reduced the number of Chinese calendars from five to two. Because of his astronomical and calendrical work, Schall von Bell was given the title Mandarin of the First Class, an honor normally reserved for Chinese dignitaries, and a sign of Schall von Bell’s influence. “It can be said,” writes a Jesuit historian, “that no westerner in the whole history of China ever enjoyed as much influence as Schall did.”¹²

Remarkable Jesuit contributions were not confined to the sixteenth and seventeenth centuries. Several Jesuits connected with the Zikawei Observatory would make important contributions into the twentieth century. Marc Dechevrens (1845-1923) became director of Zikawei in 1876. With fellow Jesuits Francisco Faura and Jose Maria Algue, Dechevrens was one of “the first to study the nature and characteristics of typhoons.”¹³ An instrument he designed to measure wind velocity was installed on the Eiffel Tower for the 1889 World’s Fair.

In 1888, Stanislas Chevalier (1852-1930) succeeded Dechevrens as director of the observatory, continuing his predecessor’s work with typhoons. Chevalier also carried out a cartographic study of the Yangtze, made no less than 1200 astronomical observations, and determined the geographical coordinates of 50 Chinese towns. His research eventually led to the creation of 64 maps, earning him a medal from the Geographical Society of Paris.¹⁴ Finally, in 1920, Ernesto Gherzi (1886-1976) was appointed to Zikawei, where he studied typhoons and Chinese climatology. Gherzi was “one of the first to investigate the relationship between microseismic noise and oscillations in the atmospheric pressure.”¹⁵ He later became a member of the Pontifical Academy of Sciences.

Taken collectively, the Jesuit Chinese missions form an important chapter in the long and often complex relationship between religion and science. Joseph Needham, in his important multi-volume Science and Civilisation in China, highlights the significance of the Jesuit Chinese missions: “In the history of intercourse between civilisations there seems no parallel to the arrival in China in the 17th century of a group of Europeans so inspired by religious fervour as were the Jesuits, and, at the same time, so expert in most of those sciences which had developed with the Renaissance and the rise of capitalism.”¹⁶ When history offers us ‘no parallel,’ we should take notice.
 
 
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