The social problem incites the Belgian catholics to study scientifically the human collectivity. As early as the nineteen-eighties learned societies are ouded, seminars, congresses, lectures are organized, a review is launched. At the Catholic University of Louvain the School of Political and Social Sciences is inaugurated in 1892. The sociological approach of the problems becomes wide-spread. All this movement is prepared by the work of a pioneer: Edouard Ducpétiaux (1804-1868). He opens the way by his numerous publications and realizations in as various fields as the social inquiries, statistics, sociography, social economics, political science, criminology... The article analyses his methodology and shows place of E. Ducpétiaux among the main intellectual currents of the past century.