Political power vs "natural laws". Physiocracy and slavery

As we know, there are two basic elements in the Physiocrats? view: on the juridical plane, the belief that positive laws follow natural ones; on the economic plane, the idea that agriculture is the sole source of net product. The importance and interdependence of these two aspects also emerge with reference to the issue of slave labour and to the debate concerning its abolition. This article attempts to inquire into the ambiguities of the economic ideas of the Physiocrats, who, in theory, favored the use of free labour, but in practice were forced, out of political realism, to accept slave labor - even though it was seen as the outcome of a "sick" law. In particular, we will show that Le Mercier de la Rivi?re and Pierre Poivre, Physiocrats and colonial Intendants, gave up to the idea of the abolition of slavery, thus legitimising its continuation.