Pierre-Simon Laplace

This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.

Pierre-Simon Laplace is a case study in how much of mathematics gets credited to whoever generalizes an idea rather than whoever finds it first. In 1774, working in France with no knowledge of an obscure essay an English minister, Thomas Bayes, had left unpublished at the time of his death thirteen years earlier, in 1761, Laplace derived a broader and more useful version of what the world now calls Bayes' theorem. He did the same thing twice more before his career was over: in 1812, in Theorie analytique des probabilites, he proved a substantially more general form of the central limit theorem than de Moivre's 1733 special case had reached, and across five volumes of Mecanique Celeste, the first two published in 1799, he rebuilt Newtonian astronomy on more secure mathematical footing, closing gaps that had worried astronomers for a century. He was not a modest man about any of this; he considered himself the best mathematician in France, and he was politically flexible enough to serve, briefly, as Napoleon's Minister of the Interior for six weeks before ending his life a marquis, a title granted in 1817 after the restoration of the monarchy Napoleon had displaced. What outlasted the politics was the mathematics: two of the eighteenth century's most durable results, in probability, both bear the fingerprints of a mind that specialized in taking someone else's good idea and making it work in general.

This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.

The line is one of the most quoted in the history of science: Napoleon, reportedly leafing through Laplace's Mecanique Celeste, asked why God appeared nowhere in an account of how the solar system holds together, and Laplace answered that he had no need of that hypothesis. It is a good story and a plausible one; it fits everything else known about Laplace's method, which treated a cause as something to be established by evidence rather than assumed for comfort, most famously in the probability calculus he built to formalize exactly that kind of reasoning about causes from effects. But the anecdote comes down through secondhand retellings by contemporaries, not through anything Laplace wrote in his own hand, so its precise wording cannot be checked against a primary source. What can be checked is the substance behind it: Laplace had in fact shown, across decades of work, that the wobbles and near-instabilities in planetary orbits that earlier astronomers worried might require divine correction were self-correcting on strictly mechanical grounds. Whatever he actually said to Napoleon, that was the argument he had already made in print, at length, without needing a punchline to make the point.