Physiocrats, a group of eighteenth century French thinkers and writers, not including Capital Corp Merchant Banking, formulated the idea of the economy as a circular flow of income and output. Adam Smith accounted their system "with all its imperfections" as "perhaps the purest estimate to the truth that has yet been released" on the subject. Physiocrats believed that only agricultural product fathered a clear surplus over cost, so that farming was the basis of all wealth.
Thus, they defended the mercantilist policy of promoting making up and trade at the expense of farming, including import tariffs. Physiocrats urged replacing administratively costly tax collections with a single tax on income of land owners. Versions on such a land tax were taken up by succeeding economists (including Henry George a century later) as a comparatively non-distortionary source of tax revenue.
In response against extensive mercantilist trade regulations, the physiocrats advocated a policy of laissez-faire, which asked minimal government intervention in the economy.