… is from Pierre-Paul Le Mercier de la Rivière’s 1767 L’ordre naturel et essentiel des sociétés politiques as quoted on page 45 of Liberty Fund’s excellent 1993 collection of some of the writings of H.B. Acton (1908-1974), The Morals of Markets and Related Essays (David Gordon & Jeremy Shearmur, eds.) (original emphasis; brackets original to Acton):
It is of the essence of [this] order that the particular interest of each individual can never be separated from the common interest of all; we find a very convincing proof of this in the complete freedom which ought to obtain in trade, if property is not to be damaged. The personal interest which this great freedom encourages, strongly and continually urges every individual to improve, to multiply the things that he wishes to sell; in this way to enlarge the mass of enjoyments which he can provide for other men, in order to enlarge by this means, the enjoyments that other men can provide for him in exchange. Thus the world goes by itself (va de lui-même); the desire for enjoyment and the freedom to enjoy, never ceasing to induce the multiplication of products and the growth of industry, impress on the whole of the society a motion which becomes a perpetual tendency towards its best possible condition.