In the literature we see an ongoing debate about the position in the history of economic thought, of François Quesnay's Tableau écommique. According to some, the development of the Tableau has made Quesnay one of the greatest economists of all time. Others, on the other hand, view the Tableau rather in terms of an interesting effort which lacks any real significance. Professor Samuelson, in his work, seems to occupy an intermediate position.

In this paper we hope to show that by looking at Quesnay's work in connection with that of Achylle-Nicolas Isnard, a direct successor and critic, the greatness and novelty of Quesnay will become apparent. Isnard employed Quesnay's views on circularity, but as opposed to Quesnay he emphasised the productivity of all sectors of the economy. By presenting a novel mathematical presentation of Isnard's work, we will show that his work is extremely relevant in order to interpret and unify present-day efforts regarding circular-flow types of models, including today's input-output models. In this sense, we aim to provide a direct link from the Tableau to modern theory.