Pierre-Simon Laplace, 1749-1827 : A Life in Exact Science

By Charles Coulston Gillispie, Robert Fox, and Ivor Grattan-Guinness

Princeton University Press [1977], 304 p.
Princeton University Press Online

This book is a republication of a Topical Essay in the 1978 Supplement I (Volume XV) of the 16 volume "Dictionary of Scientific Biography" (Charles Scribner and Sons, 1970-1980) with revisions based on the incorporation of a number of studies that have appeared since the initial publication.

The book consists of five parts, the first four describing chronologically separable stages of Laplace's scientific life, and a final section by Prof. Grattan-Guinness on the Laplace transform. The first three were written by Prof. Gillispie, and treat the periods: (I) 1768-1778, extending from Laplace's departure for Paris at age 19 to his recognition as one of the leading figures of the Academy of Science; (II) 1778-1789, during which he introduced and developed the mathematical techniques that were the basis of his great treatises, extending up to the time of the French Revolution and; (III) 1789-1805, characterized by the synthesis of his work in the publication of Exposition du système du monde and the first four volumes of Traité de mécanique céleste, and the emergence of his scientific statesmanship through the advising of government agencies and the formulation of the metric system. The final section (four chapters by Prof. Fox and three by Prof. Gillispie) covers the period 1805-1827, when Laplace addressed specific problems in physics with his disciples in the Société d'Arcueil, through his ultimate loss of influence and death.

This monograph format is more much convenient than the tightly spaced form of the original 1978 Topical Essay, and the addition of an index, a page-numbered table of contents, and page breaks between Chapters, Parts, and Appendices makes the material much easier to absorb and interrelate. Much of the material has been transcribed directly from the 1978 Topical Essay, but there are significant additions and revisions. For example, Laplace kept copies of his own letters in his extensive correspondence with leading contemporary scientists, but it had long been thought that the bulk this material had been destroyed when a fire swept the family château in 1925. In fact, it has been discovered recently that many manuscripts survived that fire, and now exist in a depository that was available for study in the preparation of this revision.

The main body of the book is characterized by an attempt to speak to us through the thoughts of Laplace. These are expressed to us through the interpretation of his writings in his own notation, in terms of the knowledge that was available to him in his time, and with no references to modern insights or implications that might break the historical context, mood, or ambiance. Attempts to connect the thoughts of Laplace to modern knowledge are thus reserved for discussion in a conclusion section near the end of the book.

The impression of Laplace that comes through these detailed analyses of his mémoires and publications is of a tireless calculator, manipulating and reformulating expressions through many pages of differentiation, integration, expansion, and numerical evaluation. However, in contrast to his predecessors and contemporaries, he did not seek elegance, rigor, or generality. Instead he sought to bend the mathematics to yield the content of his question. He was a master of approximation, of formulating rapidly convergent series, of justifying the neglect of inconvenient quantities, and of obtaining mathematical expressions that describe a multitude of physical phenomena. It is not clear whether he saw how to make an analysis come out before deciding which phenomena to handle, or the other way about, but the alternatives are probably two aspects of the same talent. Laplace's role is described as unique among scientists of his stature in that he never sought to change the world picture into which he was born, but rather to perfect it. He had no notion of changing the Newtonian system of the world, but instead to deepen it and to demonstrate its stability though mathematical analysis.

A recurring theme in the book is Laplace's lifelong tendency to couple the sciences of probability and astronomy. Consistent with the spirit of Laplacian determinism, probability was viewed as a means of repairing the defects in knowledge. However, there are tantalizing passages scattered throughout his writings that suggest that Laplace may have had an inkling (or perhaps a repressed belief) that there are inherently random processes in nature that are not merely the result of our ignorance. It is pointed out that at least one aspect of Laplace's legacy "pried open the first chink in the armor of a determined universe." His application of probability to demography and actuarial determination inspired his Paris visitor Adolphe Quetelet to formulate "Social Physics" and thereby to found the statistical social sciences. This subsequently led (through his reading of an essay on Quetelet's work by John Herschel) James Clerk Maxwell to adopt a strategy using Laplace's law of errors to specify his kinetic theory of gases.

The role of Laplace in the École Normale in 1795 is especially interesting. In this short-lived post-revolutionary experiment in public education, "only a small proportion of the fourteen hundred pupils assembled in haste to overcrowd the auditorium could have understood his lectures. His listeners ranged in age from extreme youth to near senility and in preparedness from virtual illiteracy to the genius of the young Fourier." Despite the general failure of this educational experiment, the experience resulted in a book that is one of the most successful works of science ever composed - Exposition du système du monde. Here "Laplace spares his readers nothing but the mathematics, and of that only the calculations and formulations, not the vocabulary or the reasoning." It has been said that "it is familiar without being vague, it is precise without being abstruse; its matter is drawn from a vast stock deposited in the mind of the author." Laplace seems to have set the tone for the mathematicians and scientists who were to follow him, who were no longer found in the royal courts or the salons of the aristocracy, but as teachers in the learned academies. This account is reminiscent of the "Feynman Lectures" project of our own time, in which a paradigm-shifting genius sought to make his vision of the world accessible to the beginning student, but was perhaps even more successful at inspiring the imagination of the entire community of practicing scientists.

The book provides a scholarly and human view of the scientific life of Laplace, seen through the intellectual, political, and social environment of his time. An extensive and updated bibliography together with a lively literary style makes it valuable both as a reference source and as a biographical narrative.