Eric Brian is full professor at Ecole des hautes études en sciences sociales in Paris. He is studying uncertainty and regularity of social phenomena, and in particular how scientists have caught and conceived them as objects of mathematics or social and economical sciences. He is the head of the Department of History in the French National Institute for Demography (INED) and the editor of the Revue de synthèse (Springer).A graduate of Ecole Polytechnique, he completed PhDs in applied mathematics (Orsay, 1986) and social sciences (EHESS, 1990). He has been fellow of the Harriman Institute at Columbia University (1984-1987), of the Swedish Collegium for Advanced Study (1994), of the Wissenschaftskolleg zu Berlin (2002-2003), and guest professor at the University of Vienna (1997-2002), at the Technische Universit&a Berlin (2003-2004) and the University of Geneva (2010).Among his publications are La Mesure de l'Etat. Administrateurs et géomètres au XVIIIe siècle (Albin Michel, 1994), The Descent of Human Sex-ratio at Birth. A Dialogue between Mathematics, Biology and Sociology (Springer, 2007), Le Sexisme de la première heure. Hasard et sociologie (Raisons d'agir, 2007) and Comment tremble la main invisible. Incertitude et marchés (Springer, 2009).