Productive activities and the wealth of nations: some reasons for Quesnay's failure and Smith's success

The opposition between productive activity (agriculture) and unproductive ones (the others) underlies the Tableau économique. Smith borrows Quesnay's theory of production but deeply transforms it into a distinction between productive and unproductive labour. In any case, it seems quite natural to relate the increase of the wealth of a nation to the relative importance of productive activities vis-à-vis unproductive ones. Quesnay and Smith both share this view. However, if Smith is perfectly right in doing so, Quesnay has failed to prove a definite relation between the fraction of the revenue spent with respect to the productive sector, on the one hand, and the level or growth of the revenue, on the other. Differences in political philosophy may account for this unequal analytical performance.