Summary : Studying the way French geographers of the enlightenment made use of systems offers a way to question the ability the field of geography had to produce rules for understanding the world. It also questions whether systems could in fact play this role and under what conditions. In the eighteenth century, at a moment when detailed observations were not available to trace the outlines of continents or to describe their relief, geographers drew on systems in a variety of ways. Almost unanimously cartographers considered systems as the ordering of information that allowed them then to construct maps. More polemically, however, in physical geography, some used systems as a way of establishing the principles that in their view underlay th...