Paul Lacombe (1834-1919) had a varied career as a historian, senior official and general inspector of libraries and archives. He was one of the most brilliant minds of his day: in 1859 he graduated as first in his class from the elite Ecole Nationale des Chartes, and he was made Chevalier de la Legion d'Honneur in 1887. In 1894, Lacombe published this groundbreaking work, which put him at the heart of the debate about l'histoire science - history served by scientific inquiry - at a time of intense controversy among historians and sociologists. Lacombe insisted on the need for the historian to make strict selections of evidence and to establish a hierarchy among facts. He also laid the foundations of a history which brings social and economic factors to the forefront of investigation. The book remains important and relevant to historians, sociologists and ethnologists.