This article presents the fiscal theories of Forbonnais (1722 to 1800) and Graslin (1727 to 1790) as a common system. A system that is the first to clearly establish the notion of progressive taxation upon goods inversely proportional with their utility. Thanks to the collation of the works of these two men with the inventories of their libraries and their arithmetic skills, this article is able to reveal their real backgrounds and influences. Finally, the progressive taxation would allow a new allocation of the factors of production that would be the key point for a whole reform of the French Kingdom.Forbonnais, Graslin, indirect taxation, geometric progression, luxury,