Pierre-Simon Laplace: Early Nineteenth Century Parisian Science

    The following is a case study of French Natural Philosophy at the beginning of the nineteenth century, focusing on Pierre-Simon Laplace. The study shows influences typical to Parisian Natural Philosophy at the beginning of the nineteenth century. Early nineteenth century Parisian Natural Philosophers were affected by their university experiences, as Laplace was at The University of Caen, by fellow scientists, as Laplace was with Newton and d’Alambert, by Napoleon, as Laplace was with his famous lack of a “God Hypothesis”, and by collaboration, as Laplace was with his work with Lavosier. All of these influences led to Laplace’s discoveries, including his probability theory and his nebular hypothesis. This shows the importance of politics, universities, and other Parisian Natural Philosophers on the development of Parisian Natural Philosophy during the early years of the nineteenth century. So while this may read as a biography, it is rather a case study of a typical French Natural Philosopher’s journey to discovery. By being written in this way, the events become more tangible and show the larger events on a micro level. Laplace is the most appropriate to look at because some have gone so far as to call him “among the most influential scientists of all time” [13].
Academia in Shaping Pierre-Simon Laplace

Pierre-Simon Laplace was a pivotal figure in the advancement of the sciences during the early nineteenth century, and influenced the future of math and physics. However, before he achieved such high esteem in the scientific community, there were many key influences that facilitated his transition. When young Laplace was recruited to study at the University of Caen, he was still working towards fulfilling the family expectation of himself. During his time at the University he was studying theology so that he could work in the church. Early on he came into contact with an abbe named Christophe Gadbled, a professor of mathematics and hydrography. It was this professor who introduced young Laplace to calculus and Newtonian physics. The curiosity was at the base of his transition to the sciences and would start to shape the way he did science in the future. [1]

Newton’s work was a major influence on Laplace’s theories. Principia was highly praised by

The acceleration a of a body is parallel and directly proportional to the net force F and inversely proportional to the mass m, i.e., F = ma.
Laplace. [6] Throughout his career as a mathematician he would constantly expand upon Newton’s theories. He further developed upon Newton’s theory of planetary motion, specifically Newton’s second law, using calculus rather than geometric reasoning. He used calculus to understand the disparities in the inclination of the “elliptic and planetary orbits, the lunar orbit, perturbations produced in the motion of the planets by the actions of their satellites.” [3] He would also point out errors in Newton’s work, such as the failure to distinguish between gaseous flow at constant temperature and at constant entropy. Because of the similarity to Sir Isaac Newton in the way he conducted science, he is often referred to as the French Newton. [2]

Without the influence of his professors it is unclear that Laplace would have gravitated

Jean le Rond d'Alembert
towards math, but rather he would most likely have maintained his course in theology. Because of his understanding and acceleration in mathematics, Laplace was introduced to the high priest of mathematics, Jean le Rond d’Alembert, who would be one of the biggest influences on the Laplacean view of math. [3] It is d’Alembert who took Laplace as a protégé and got him a teaching position at the Ecole militaire. Without d’Alemberts help Laplace would not have been able to stay in Paris to continue his studies, and he would not have become the influential Laplace we know today. [1]

Laplace heavily draws upon D’Alembert’s theories in his own works. He often began his research based on papers by his mentor. Laplace’s ‘Sur le principe de la gravitation de la universelle et sur les inegalites seculaires des planets qui en dependent’ was based on principles of motion for solid bodies which was written by d’Alembert. Even his theory of probability and statistics had its origin in the works of D’Alembert. [4] The idea that probability can be assigned in situations with equally balanced evidence and the probability of all possible outcomes is equal, was an idea both mathematicians shared. [7]

Effects of the Scientific Community on Laplace

The scientific community in Paris during the lifetime of Laplace was unique due to the political and economic activity of the time, caused by the French revolution. From 1793-1896 the University of Paris was shut down which led to many scientists working together on a personal level or in smaller universities.  After Jean le Rond d’Alembert introduced Laplace to the scientific community, due to a he wrote letter on the principles of mechanics, he would go on to have many interactions in such a fashion.[3]

Early success in Laplace’s rise to academic prowess was assisted greatly by his work done with Lavoisier developing chemistry. Laplace was six years younger and of lower academic status than Lavoisier when they started significant work. Together they conducted calorimeter experiments in the field of thermochemistry in order to prove that animals create their energy by combustion reactions. This took place before Laplace became famous for his writings on probability and gravitational physics of the solar system (his nebular hypothesis). This gave him a way to gain academic distinction allowing him to continue on his later works. [8]

Laplace held most of his interactions in the scientific community with mathematicians. Joseph-Louis Lagrange in particular worked on planetary motion at the same time as Laplace. Lagrange and Laplace had contrasting mathematic styles. Laplace cared only if his results were correct, whereas Lagrange put great emphasis on the elegance and proofs of his mathematics. [9] In 1773 Laplace read his paper on the invariability of planetary motion in front of the Academy des Sciences. That March he was elected to the academy, a place where he conducted the majority of his science. His election ignited a career long competition in which Laplace and Lagrange would try to outdo each other, though often assisting each other in their research. [10] The rest of his interactions within the Academy des Sciences were very similar to those he had with Lagrange. He rarely got along with colleagues and worked with them on a strictly business relationship. While in the academy Laplace was able to explain the universe far better than his predecessors Newton and Euler were able to. Sparked by this competition, Laplace was able to answer the great questions of the time particularly the reason for the difference in orbit between Jupiter and Saturn. [9]

A great change in the career of Laplace occurred around 1796 when he presented his nebular hypothesis that explained the origins of the universe. His body of work and interactions with Napoleon gained him many accolades and honors. From this point on he didn’t need help with his work and was able to focus on what he pleased in the early decades of the 19th century. Other scientists had very little influence on him past this time. Some younger scientists such as Fresnel, Petit and Fourier however were able to impact his works by being rivals in intelligence, forcing him to defend his previous works. At this place in time though, his scientific career was ending because he was unable to keep up with his responsibilities and old age. [10]

Laplace And Religion During Napoleon’s Reign

            Laplace’s early years were anything but ordinary, as he attended a Benedictine priory and university in Caen, and seemed destined for a life in the Church (14). Despite his ordinary upbringing, at the age of 19 Laplace rejected the life in the church his father envisioned for him and went to France to study science. In his findings, Laplace shows the world in a way that does not need to take into account the influence of a God, even telling Napoleon Bonaparte, France’s military and political leader, that “he hath no need for that hypothesis” (the presence of God) (17). However, Laplace was careful not to brand himself an atheist, as he understood the religious nature of Napoleon, and he could not risk his government position under the man by admitting his atheism (12). During this time, Napoleon had signed a concord with the Pope restoring a degree of religious presence in France, as he believed that “Christianity was the basis of all real civilization; and considered Catholicism as the form of worship most favorable to the maintenance of order and the true tranquility of the moral world” (16). Napoleon’s strict stance on religion during his powerful military reign could have easily forced Laplace to view the world taking into account God’s place as a creator and or mediator, but instead, he pursued what he believed to be the correct science. Laplace believed Isaac Newton was wrong in allowing for God to explain certain happenings of the universe, and wanted to fully explain the properties of the world without taking into account the presence and influence of God, a figure impossible to prove through calculations. While it may seem odd that he felt empowered to do this under a regime led by a man of religion, Napoleon and France’s military success actually served to empower Laplace, as he believed himself to be the “world master of physical science”, due to France’s power in Western Europe (13). As France’s power grew, so did Laplace’s. Political power and backing proves vital in the world of science, as one needs support for their research to be validated. Laplace advanced his public support with regards to religion when he published his only philosophical essay and offered the great possibility of a higher and supreme being, despite his belief that such a being was superfluous to explaining the mechanics of the world. (14). Society held Laplace in high regard, despite his theories’ controversial stance with regards to religion. As Napoleon’s power grew, Laplace’s did as well. In 1805 Laplace’s extended work in physics led him to finding the Society of Arcueil, a society focused on physics and using mathematics to explain the world around them (15). The society had many prominent members including: Alexander Von Humboldt, Antoine Lavoisier, Joseph Louis Gay-Lussac, etc. The society worked to make advances under Napoleon’s reign, as he deeply valued the importance of scientific advancement, specifically with regards to military development (18). However, eventually Laplace began to disagree with other members of the society about the fluidity of heat and light, and with the waning power of Napoleon, the society disbanded after only a couple years.


 Laplace’s Probabilistic Theory and Paris’ Reaction to it


            Laplace made a huge contribution to the study of probability when he wrote his “A Philosophical Essay on Probabilities”. In it, he listed ten Principles that still are used in modern Probability calculations. He also made one of the boldest statements of his time [11]. Towards the beginning of his essay, Laplace stated, in his Principle of Sufficient Reason, that present events are connected to past events by causes, and that nothing can occur without being caused. He argued that by using this Principle, if one can figure out the cause of an event, one could predict the future. This was a revolutionary scientific claim [11]. Laplace also laid out 10 Probability principles, which are as follows:


  1. Probability is the ratio of favorable cases to possible cases.
  2. The first probability only applies when all possible events have an equal likelihood of occurring. When this is not the case, the probability of each event must be calculated and then the probability of the event is the sum of the probability of each individual attempt.
  3. If all the events are independent of one another, the probability of any sequence of events occurring is the product of the probability of each individual attempt.
  4. For dependent events, the probability of one event, event A, occurring after another event, event B, is the probability of event B times the probability of both event A and event B occurring.
  5. The probability that an event, event A, will occur given that another event, event B, has already occurred, is the ratio of the probability of event A and B occurring to the probability of just event B occurring. (A&B/B).
  6. The probability of any one of many events occurring is the ratio where the numerator is the probability of any of these events resulting from a cause and the denominator being the sum of all the individual events’ probabilities.
  7. The probability of a future event occurring is the sum of the products of the probability of each cause of the events.
  8. The probability of a sequence of events is the sum of the products of each individual events probability.
  9. In a set of favorable and unfavorable events, the advantage which results is the ratio of the sum of the products of the probability of the favorable events to the sum of the products of the probability of the unfavorable events.
  10. The absolute value divided by the total benefit, in regards to the person interested; of an event is the relative value of an infinitely small sum. [11]



These principles were surprisingly quietly received, as Laplace stayed out of French politics, for the most part, during the early parts of his career. When these principles were openly talked about, Laplace was more involved in French affairs, but due to his high academic standing, his work was relatively well accepted [13].


Works Cited

[1] Tore Frangsmyr, J. L. Heilbron, and Robin E. Rider, editors, The Quantifying Spirit in the EighteenthCentury. Berkeley:  University of California Press,  c1990 1990. http://ark.cdlib.org/ark:/13030/ft6d5nb455/

 [2] Christopher John Murray, editor, Encyclopedia of the Romantic Era, 1760 -1850. New York & London: Fitzroy Dearborn. 2004. 


 [3] Charles Coulston Gillispie, Pierre-Simon Laplace, 1749-1827: a life in exact science. Princeton: Princeton University Press, 1997. 125-139

 [4] Thomas L. Hankin, Jean d’Alembert: Science and the Enlightenment. Oxford University Press, 1970.http://books.google.com/books?id=gwjc3vGW9-MC&printsec=frontcover#v=onepage&q&f=false

[6] Baron Henry Brougham and Vaux, Edward John Routh, Analytical View of Sir Isaac Newton’s Principia. London: Longman, Bown, Green, and Longmans: 1855.http://books.google.com/books?id=oM82AAAAMAAJ&pg=PA330&lpg=PA330&dq=laplace+principia&source=bl&ots=_qZlqk57rO&sig=VxqL9fNopph1ZUJ8CmAFadxldHg&hl=en&ei=PdDmTruZPIj1gAeSyeT-CA&sa=X&oi=book_result&ct=result&resnum=1&ved=0CCQQ6AEwAA#v=onepage&q&f=false

[7] Jean D’Alembert, "Reflections on the Calculus of Proababilites". Opuscules Mathematiques: Volume II, Tenth Memoir, pp. 1-25.http://www.cs.xu.edu/math/Sources/Dalembert/memoir10.pdf


[8] Henry Guerlac  Historical Studies in the Physical Sciences , Vol. 7, (1976), pp. 193-276

[9] A Short Account of the History of Mathematics by W. W. Rouse Ball (4th Edition, 1908). http://books.google.com/books?id=egY6AAAAMAAJ&pg=PA412&source=gbs_toc_r&cad=4#v=onepage&q&f=false

[10] O'connor, JJ, and EF Robertson. "Pierre Simon Laplace." University of St Andrews, Scotland. Accessed December 7th, 2011 http://www.gap-system.org/~history/Biographies/Laplace.html.

[11] Simon Laplace, Pierre. A Philosophical Essay on Probabilities. New York: Wiley, 1902. 16-37

[12] Campisi, Judith. "LaPlace and the Superfluous God: Political Correctness in the Age of Reason."  Berkeley Emeriti Times, 22 Jan. 2005. Web.      <http://thecenter.berkeley.edu/pdf/ucbeajan05.pdf>.

[13] Crosland, Maurice. "A Science Empire in Napoleonic France." (2006). EBSCOhost. Web.             <http://web.ebscohost.com.ezproxy.library.wisc.edu/ehost/pdfviewer/pdfviewer?sid=fe17f177-6b97-447d-9f7a-474dbc00c594%40sessionmgr11&vid=4&hid=13>.

[14] Hahn, Roger. "Pierre Simon Laplace: A Determined Scientist." 2005 (378-384). 

[15] "Laplace Biography." Web. 13 Dec. 2011. <http://www.gap-system.org/~history/Biographies/Laplace.html>.

[16] "Napoleon's Personal Feelings about Religion." Roy Rosenzweig Center for History and New  Media. Web. 13 Dec. 2011. <http://chnm.gmu.edu/revolution/d/505/>.

[17] "The Quantifying Spirit in the 18th Century." UC Press E-Books Collection, 1982-2004. Web. 13   Dec. 2011. <http://publishing.cdlib.org/ucpressebooks/view?docId=ft6d5nb455>.

[18] Williams, Pearce L. "Science, Education, and Napoleon and I." ISIS (1956). (24-48)

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