until it reaches a maximum." This was a recognition that the productivity gains required to increase national wealth had an ultimate limit, and, therefore, wealth could not be infinite. Investment capital Both Quesnay and Anne Robert Jacques Turgot, Baron de Laune recognized that capital was needed by farmers to start the production process, and both were proponents of using some of each year's profits to increase productivity. Capital was also needed to sustain the laborers while they produced their product. Turgot recognizes that there is opportunity cost and risk involved in using capital for something other than land ownership, and he promotes interest as serving a "strategic function in the economy.” Subsequent developments The ideas of the Physiocrats had an influence on Adam Smith, David Ricardo, John Stuart Mill, and above all Henry George, who appears at first to have come to similar beliefs independently. George was the driving force behind what became known as the Single Tax movement (not to be confused with Flat Tax). The Single Tax is a proposal for the use of the annual rental value of land (land value taxation) as the principal or sole source of public revenue. The New Physiocratic League is a current Georgist political movement which seeks to revive elements of physiocracy. See also Agrarianism Classical economics Classical liberalism Flour War Free market French Liberal School Geolibertarianism Georgism Jeffersonian democracy Land value tax People Richard Cantillon François Quesnay Anne Robert Jacques Turgot Jean Claude Marie Vincent de Gournay Victor de Riqueti, marquis de Mirabeau Honoré Gabriel Riqueti, comte de Mirabeau Pierre Samuel du Pont de Nemours Pierre-Paul Lemercier de La Rivière de Saint-Médard Nicolas Baudeau Henry George Notes References Charbit, Yves; Arundhati Virmani (2002) "The Political Failure of an Economic Theory: Physiocracy", Population, Vol. 57, No. 6. (Nov. – Dec., 2002), pp. 855–883, Institut National d'Études Démographiques "Theories of Surplus Value" from the Economic Manuscripts of 1861–1863" contained in Collected Works of Karl Marx and Frederick Engels: Volume 30, New York: International Publishers, 1988. Gide, Charles and Charles Rist,A History of Economic doctrine from the time of the Physiocrats to the present day. 1915 Muller, A. L. (1978) Quesnay's Theory of Growth: A Comment, Oxford Economic Papers, New Series, Vol. 30, No. 1., pp. 150–156. Spiegel, Henry William (1983), The Growth of Economic Thought, Revised and Expanded Edition, Duke University Press Steiner, Phillippe (2003) "Physiocracy and French Pre-Classical Political Economy", Chapter