Geoffroi Jacques Flach (February 16, 1846 – December 4, 1919) was a French jurist and historian born at Strasbourg, Alsace, of a family known at least as early as the 16th century, when Sigismond Flach was the first professor of law at University of Strasbourg. G.J. Flach studied classics and law at Strasbourg, and in 1869 took his degree of doctor of law. In his theses as well as in his early writings such as De la subrogation réelle, La Bonorum possessio, and Sur la durée des effets de la minorité (1870) he endeavored to explain the problems of laws by means of history, an idea which was new to France at that time. The Franco-Prussian War engaged Flach's activities in other directions, and he spent two years (described in his Strasbourg après le bombardment, 1873) at work on the rebuilding of the library and the museum, which had been destroyed by Prussian shells. When the time came for him to choose between Germany and France, he settled definitely in Paris, where he completed his scientific training at the École des Chartes and the École des Hautes Études. Having acted for some time as secretary to Jules Sénard, ex-president of the Constituent Assembly, he published an original paper on artistic copyright, but as soon as possible resumed the history of law. In 1879 he became assistant to the jurist Édouard René de Laboulaye at the Collège de France, and succeeded him in 1884 in the chair of comparative legislation. Since 1877 he had been professor of comparative law at the free school of the political sciences. To qualify himself for these two positions he had to study the most diverse civilizations, including those of the East and Far East (e.g. Hungary, Russia and Japan) and even the antiquities of Babylonia and other Asiatic countries. Some of his lectures have been published, particularly those concerning Ireland: Histoire du régime agraire de l'Irlande (1883); Considérations sur l'histoire politique de l'Irlande (1885); and Jonathan Swift, son action politique en Irlande (1886). His chief efforts, however, were concentrated on the history of ancient French law. A celebrated lawsuit in Alsace, pleaded by his friend and compatriot Ignace Chauffour, aroused his interest by reviving the question of the origin of the feudal laws, and gradually led him to study the formation of those laws and the early growth of the feudal system. His great work,