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viction it bases the first theoretical account of the relations between the rural economy and population. Following Adam Smith, who believed that no one had come closer to the truth in the field of political economy than the Physiocrats, they are generally acknowledged as the first to have developed a coherent economic theory. They achieved a major theoretical advance by creating a model of demo-economic growth based on the income of landed capital — they called it "the net product" — which inspired Marx to develop the concept of surplus valued. For the Physiocrats, agricultural production regulates population; more specifically, the number of men, their geographical distribution, and their living conditions, are determined by the land rent. Classical political economy (in the work of Smith and later of Malthus and Ricardo) took up this idea, but extended it to all sectors of economic activity. The level of production regulates the size of the population, and the adjustment takes place in the labour market through the wage rate.
The "Physiocratic movement" developed under its leader, François Quesnay (1694-1774)(3). He had few disciples. Marquis Victor Riqueti de Mirabeau (1715-1789), father of the famous revolutionary, publishes L'Ami des hommes ou Traité de la population, which will be widely distributed and read, in 1756. Less well known are Pierre Mercier de La Rivière (1720-1793), Guillaume-François Le Trosne (1728-1780), the Abbé Nicolas Baudeau (1730-1792), and Pierre-Samuel Dupont de Nemours (1739-1817). Their loyalty to the master's thought, or rather their rigid orthodoxy, means that the essence of Physiocratic thought is in fact contained in the writings of Quesnay, particularly the articles published in the Encyclopédie^.
For the diffusion of their doctrines, the Physiocrats rely on several periodicals, and in particular the Ephémérides du citoyen published between 1765 and 1772. They make followers among rulers in Europe and beyond — the Grand Duke of Tuscany, the Margrave of Baden, Catherine II
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A large literature exists on the place of the Physiocrats in economic thought, which is beyond the scope of this study. Schumpeter (1997) considers Quesnay superior to Adam Smith on several points and evaluates his contribution to economic analysis very positively. For a more complete discussion of certain concepts and possible affinities with other currents, see Meek, 1962, especially the second half of the volume (concerning, for example, the theory of profit, the general Walrasian equilibrium, hoarding and the multiplier in Keynes, the theoreticians of underconsumption, and more generally the convergences and divergences with classical English political economy). For the influence of Quesnay on Adam Smith, see Ross, 1984. On the doctrine of sterile classes and the resulting contradictions for the analysis in terms of flow, see Herhtz, 1961. On the theory of fundamental price, which paved the way for Adam Smith, and on the analysis of the role of different classes in production, cf. Vaggi, 1987, pp. 58-93, 169-173. On the Physiocratic origins of Jean-Baptiste Say's law of markets, see Spengler, 1945a and 1945b. On the reformulation of the Tableau économique as a Léontief matrix, see Phillips, 1955. On Marx, see Malle, 1976. (3) Weulersse, 1910, vol I and vol. II. On Quesnay himself, one may consult the richly detailed biography drawn up by Jacqueline Hecht, 1958. (4> Some of their contemporaries accused them of being a sect. Given the numerous repetitions from one author to another, we will regroup the references to the writings of the different Physiocrats in a note at the end of each paragraph. For Quesnay's works, all references are to the INED edition.