International audienceThis paper does not focus on models proper, but on the notion of modelisation as a creative process and a solution to one of the key issues of XIXth century's intellectual life : how can one grasp both the one and the many at the same time? The answer lies in two specific areas within which naturalism can be considered "abstract": the theory of characters, as redefined by Zola through a statistical approach of "types" (Quetelet) ; the graphic sketches that served as the bases of Rougon-Macquart's genesis, and make scientific models appear as fiction-shifters. At the intersection of these areas, the formal play unveils itself as a so-said scientific justification for reactivating popular knowledges despised by official ...