Laplace, Pierre-Simon (1749–1827)

In company with Lagrange and Legendre, Laplace was one of the three foremost mathematicians during the half-century of French pre-eminence in science, from the 1770s into the 1820s. Although he invented or developed many mathematical techniques for solving various classes of problems, most notably generating functions, the Laplace transform, the Laplace expansion, the variation of constants, and the generalized gravitational function, he was more interested in what he could do with mathematics than with mathematics itself. His main treatises are Mécanique céleste (Celestial Mechanics) and Théorie analytique des probabilités (Analytical Theory of Probability). In addition he published Exposition du système du monde (Exposition of the System of the World) and Essai philosophique sur les probabilités (Philosophical Essay on Probability). Not exactly popularizations, the latter pair were verbal explanations of the two bodies of subject matter intended for a well-educated public. Both have gone through many editions. Though unrelated in content, the two main branches of Laplace’s work were related philosophically, celestial mechanics being concerned with the structure of the world, and probability with what we can know about it. In both respects Laplace’s motivation was to vindicate the Newtonian system of the world. In the later half of his life he developed an interest in physics and may be considered the impresario if not quite the founder of mathematical physics. He more than any other was responsible for the design of the metric system of weights and measures, a worldwide legacy of the French Revolution. A favourite of Napoleon, Laplace was a principal statesman of science during the Napoleonic period and afterwards.