work to dispose of beyond what he himself has occasion for; and every other workman being exactly in the same situation, he is enabled to exchange a great quantity of his own goods for a great quantity, or, what comes to the same thing, for the price of a great quantity of theirs. He supplies them abundantly with what they have occasion for, and they accommodate him as amply with what he has occasion for, and a general plenty diffuses itself through all the different ranks of society. (The Wealth of Nations, I.i.10) The neoclassical interest in Smith's statement about "an invisible hand" originates in the possibility of seeing it as a precursor of neoclassical economics and its concept of general equilibrium; Samuelson's "Economics" refers six times to Smith's "invisible hand". To emphasise this connection, Samuelson quotes Smith's "invisible hand" statement substituting "general interest" for "public interest". Samuelson concludes: "Smith was unable to prove the essence of his invisible-hand doctrine. Indeed, until the 1940s, no one knew how to prove, even to state properly, the kernel of truth in this proposition about perfectly competitive market." Very differently, classical economists see in Smith's first sentences his programme to promote "The Wealth of Nations". Using the physiocratical concept of the economy as a circular process, to secure growth the inputs of Period 2 must exceed the inputs of Period 1. Therefore, those outputs of Period 1 which are not used or usable as inputs of Period 2 are regarded as unproductive labour, as they do not contribute to growth. This is what Smith had heard in France from, among others, François Quesnay, whose ideas Smith was so impressed by that he might have dedicated The Wealth of Nations to him had he not died beforehand. To this French insight that unproductive labour should be reduced to use labour more productively, Smith added his own proposal, that productive labour should be made even more productive by deepening the division of labour. Smith argued that deepening the division of labour under competition leads to greater productivity, which leads to lower prices and thus an increasing standard of living—"general plenty" and "universal opulence"—for all. Extended markets and increased production lead to the continuous reorganisation of production and the invention of new ways of producing, which in turn lead to further increased production, lower prices, and improved standards of living. Smith's central message is, therefore, that