The Physics of Society Statistics

concepts The physics of society Statistics

By seeking to uncover the rules of Births and deaths were a major preoccupa- Philip Ball tion of early social statisticians, including the collective human activities, today’s he introduction of probability into the astronomer Edmund Halley. In 1781, Laplace statistical physicists are cautiously fundamental nature of the quantum tallied male and female births in Paris, aiming to return to their roots. Tworld by Bohr, Born and Schrödinger in explaining their near-equality as merely the the 1920s famously perplexed some scholars result of a random process, rather than, as was of science’s philosophical foundations. But previously thought, a sign of divine wisdom. fertile study, and not mere brainspinning”. arguments about chance, probability and Laplace showed that variations in such Others dismissed the idea that people’s determinism were no less heated in the mid- social statistics could be described by a univer- actions are governed by laws. At times, Buckle nineteenth century, when statistical ideas sal ‘error curve’, which was introduced in 1733 seemed to imply a compulsion whereby entered classical physics. by the mathematician Abraham de Moivre to individuals would find themselves acting in a James Clerk Maxwell allowed probabilistic describe the results of coin tossing. The ubiq- certain way to fulfil ‘quotas’. Ralph Waldo physics to bring him to the verge of mysticism: uity of this curve, now familiar as the gaussian, Emerson mocked what he saw as the absurd “It is the peculiar function of physical science was then seen as miraculous: a natural law that rigidity of the idea: “Punch makes exactly one to lead us to the confines of the incomprehen- applies as much to human affairs as to errors capital joke per week; and the journals con- sible, and to bid us behold and receive it in in measuring planetary motion. trive to furnish one good piece of news every faith, till such time as the mystery shall open.” The idea that society is governed by laws day.” In Notes From the Underground, Dosto- The use of statistics as a mathematical tool of as precise as those of physics was a product evsky had Buckle in mind when his narrator all the sciences provoked passionate responses of the Enlightenment, and was espoused by raves that man would rather make himself from philosophers, novelists and social Immanuel Kant and the political philoso- mad than be constrained by law-like reason. commentators. Few scientific issues besides pher Auguste Comte. When the Belgian Maxwell concluded that the error curve is darwinism (itself given a statistical treatment astronomer Adolphe Quetelet came to the the signature of all random processes, and of by Darwin’s cousin Francis Galton) attracted French Royal Observatory in 1823, he was processes that, although deterministic, are too such debate in parlours and periodicals. captivated by Laplace’s statistical regularities complex to be reduced to newtonian terms. So It was not physicists who started this fuss and began to argue in favour of what Comte the gaussian curve was the natural choice for but sociologists, who found that chance and later called “social physics”. Quetelet’s popu- the velocity distribution in his kinetic theory, randomness in the world of people and larization of Laplace’s data impressed the and the statistics of social physics thus helped politics, far from banishing predictability and likes of John Herschel and John Stuart Mill. to launch statistical mechanics. Ludwig Boltz- making social science oxymoronic, seemed to But the most visible exposition of these mann also drew on the analogy with the have laws of their own. This, to widespread dis- laws was given in the epic (and misnamed) statistical regularities of Quetelet and Buckle may, seemed to challenge the idea of free will. History of Civilization in England (1857–61) when he extended Maxwell’s work on mol- In the seventeenth century, Sir William by Henry Thomas Buckle, who believed that ecular probability distributions in 1872. Petty recognized that the study of society historical events occurred with a law-like There is a pleasing symmetry to the way in could only hope to emulate the precision of inevitability. “The great truth,” he said, “is which today’s statistical physicists cautiously science if it became quantitative. Petty’s call that the actions of men ... are in reality never seek to extend their models and concepts into for a ‘political arithmetic’ induced his friend inconsistent, but however capricious they social science, such as pedestrian and traffic John Graunt in the 1660s to advocate ‘social may appear only form part of one vast system movement and descriptions of the economy. numbers’ as a way to guide political policy. of universal order.” One of the book’s earliest Statistical methods are hereby returning, Graunt compiled mortality tables, reasoning readers was Maxwell, who found it “bump- much refined, from whence they came. that good legislation and government are tious” but remarked that it contains “a great The statistical nature of quantum

VICKY ASKEW impossible without such demographic data. deal of actually original matter, the result of mechanics is different from that of classical physics, as it invokes variables with values that are not merely unknown but unknowable. Nonetheless, quantum probability would have had a rockier path if physicists had not been prepared by the knowledge that a statistical approach does not preclude the existence of precise laws. As early as 1918, the physicist Marian Smoluchowski considered probability to be central to modern physics: “Only Lorentz’s equations, electron theory, the energy law, and the principle of relativity have remained unaffected, but it is quite possible that in the course of time exact laws may even here be replaced by statistical regularities.” I Philip Ball is a consultant editor of Nature.

FURTHER READING Porter, T. M. The Rise of Statistical Thinking 1820–1900 (Princeton Univ. Press, Princeton, 1986). Olson, R. G. Science Deified and Science Defied Vol. 2 (Univ. California Press, Berkeley, 1995).