QUETELET, (LAMBERT) ADOLPHE (JACQUES)

born Feb. 22, 1796, Ghent died Feb. 17, 1874, Brussels Belgian mathematician, astronomer, statistician, and sociologist known for his application of statistics and the theory of probability to social phenomena. Quetelet studied astronomy at the Observatory of Paris and the theory of probability under Pierre-Simon Laplace. He lectured at the Brussels Athenaeum, military college, and museum. He founded (1828) and directed the Royal Observatory, Brussels; served as perpetual secretary of the Belgian Royal Academy (183474); and organized the first International Statistical Congress (1853). For the Dutch, and later the Belgian, government he collected and analyzed statistics on crime, mortality, and other subjects and devised improvements in census taking. He also developed methods for simultaneous observations of astronomical, meteorological, and geodetic phenomena from scattered points throughout Europe. In Sur l'homme (1835; A Treatise on Man and the Development of His Faculties, 1842), republished in 1869 as Physique sociale, he presented his conception of the homme moyen (average man) as the central value about which measurements of a human trait are grouped according to the normal probability curve. His studies of the numerical constancy of such presumably voluntary acts as crimes stimulated extensive studies in moral statistics and wide discussion of free will versus social determinism. In trying to discover through statistics the causes of acts in society, Quetelet conceived of the relative penchant (propensity; e.g., to crime) of specific age groups. This idea, like his homme moyen, evoked great controversy among social scientists in the 19th century.