MIA: Encyclopedia of Marxism: Glossary of Organisations
Quesnay and other French writers of the 1750s and 1760s were the first economists to begin to analyse production rather than simply circulation in the endeavour to find the source of surplus value. They believed however that only agricultural labour was truly productive. Value extracted from Nature by agricultural labour is distributed by circulation and manufacturing is simply the utilisation of labour supported by the surplus product of the land for other activities more or less akin to circulation, in much the way Marx regarded domestic service as expenditure of surplus rather than productive labour.
"As the actually first systematic spokesmen of capital, [the physiocrats] attempt to analyse the nature of surplus-value in general. For them, this analysis coincides with the analysis of rent, the only form of surplus-value whch they recognise. Therefore, they consider rent-yielding, or agricultural, capital to be the only capital producing surplus-value, and the agricultural labour set in motion by it, the only labour producing surplus-value, which from a capitalist point of view is quite properly considered the only productive labour. .. pushing into the background in favour of its own practical interests the beginnings of scientific analysis made by Petty. ... The physiocrats, furthermore, are correct in stating that in fact all production of surplus-value, and thus all development of capital, has for its natural basis the productiveness of agricultural labour". [Capital Vol III, Ch XLVII]
In the Physiocrats we see the naïve-materialist conception that only Nature, not human labour, can be the source of value; it is this naïveté which is criticised in Hume's scepticism. Also, we see the Physiocrats promoting what Marx refers to as their "own practical interests". The promotion of their specific property as the source of value by the theoretical representatives of a class is also seen in the early Merchantile and Monetarist systems, and to this day, for instance, among finance capitalists who believe that "money makes money" or industrialists who see all the service sectors as parasitic in relation to their own "real" productivity. For French political economy of the late eighteenth and early nineteenth century, no distinction was made between the capitalist farmer and the agricultural labourer or between the industrial worker and the industrial capitalist; the capitalist was everywhere taken as the producer, in the way that we say "Hadrian built a wall".