Adam Smith's writing on his invisible hand

■ Source 1: http://en.wikipedia.org/wiki/Invisible_hand

In economics, the invisible hand, also known as invisible hand of the market, is the term economists use to describe the self-regulating nature of the marketplace.[1] This is a metaphor first coined by the economist Adam Smith in The Theory of Moral Sentiments, and used a total of three times in his writings. For Smith, the invisible hand was created by the conjunction of the forces of self-interest, competition, and supply and demand, which he noted as being capable of allocating resources in society.[2] This is the founding justification for the Austrian laissez-faire economic philosophy, but is also frequently seen in neoclassical and Keynesian economics. The central disagreement between economic ideologies is, in a sense, a disagreement about how powerful the "invisible hand" is. [2]

Adam Smith uses the metaphor in Book IV, chapter II, paragraph IX of The Wealth of Nations. In the often misquoted and poorly understood paragraph quoted below[,] Smith argues that a preference for the use of "domestic" industry over "foreign" industry to gain individual profit constitutes an "invisible" and benevolent hand which promotes the interests of the nation and society at large while at the same time enriching the individual. The individual may have a selfish motive but the use of domestic industry and labor enriches and promotes the interests of society as a whole.

By preferring the support of domestic to that of foreign industry, he intends only his own security; and by directing that industry in such a manner as its produce may be of the greatest value, he intends only his own gain, and he is in this, as in many other cases, led by an invisible hand to promote an end which was no part of his intention. Nor is it always the worse for the society that it was not part of it. By pursuing his own interest he frequently promotes that of the society more effectually than when he really intends to promote it. I have never known much good done by those who affected to trade for the public good. It is an affectation, indeed, not very common among merchants, and very few words need be employed in dissuading them from it.

(... continued on the source link above) 

■ Source 2: http://en.wikipedia.org/wiki/The_Wealth_of_Nations

Chapter 2[of the Book 4]'s full title is "Of Restraints upon the Importation from Foreign Countries of such Goods as can be Produced at Home". The "Invisible Hand" is a frequently referenced theme from the book, although it is specifically mentioned only once.

"As every individual, therefore, endeavors as much as he can both to employ his capital in the support of domestic industry, and so to direct that industry that its produce may be of the greatest value; every individual necessarily labours to render the annual revenue of the society as great as he can. He generally, indeed, neither intends to promote the public interest, nor knows how much he is promoting it. By preferring the support of domestic to that of foreign industry, he intends only his own security; and by directing that industry in such a manner as its produce may be of the greatest value, he intends only his own gain, and he is in this, as in many other cases, led by an invisible hand to promote an end which was no part of his intention. Nor is it always the worse for the society that it was no part of it. By pursuing his own interest he frequently promotes that of the society more effectually than when he really intends to promote it." (Book 4, Chapter 2)

■ Source 3: Chapter 2 of the Book 4 of Adam Smith's The Wealth of Nations

Book IV: On Systems of Political Economy

Chapter II: On Restraints upon the Importation from Foreign Countries of such Goods as can be produced at Home

(...) Secondly, every individual who employs his capital in the support of domestic industry, necessarily endeavours so to direct that industry that its produce may be of the greatest possible value.

The produce of industry is what it adds to the subject or materials upon which it is employed. In proportion as the value of this produce is great or small, so will likewise be the profits of the employer. But it is only for the sake of profit that any man employs a capital in the support of industry; and he will always, therefore, endeavour to employ it in the support of that industry of which the produce is likely to be of the greatest value, or to exchange for the greatest quantity either of money or of other goods.

But the annual revenue of every society is always precisely equal to the exchangeable value of the whole annual produce of its industry, or rather is precisely the same thing with that exchangeable value. As every individual, therefore, endeavours as much as he can both to employ his capital in the support of domestic industry, and so to direct that industry that its produce may be of the greatest value; every individual necessarily labours to render the annual revenue of the society as great as he can. He generally, indeed, neither intends to promote the public interest, nor knows how much he is promoting it. By preferring the support of domestic to that of foreign industry, he intends only his own security; and by directing that industry in such a manner as its produce may be of the greatest value, he intends only his own gain, and he is in this, as in many other cases, led by an invisible hand to promote an end which was no part of his intention. Nor is it always the worse for the society that it was no part of it. By pursuing his own interest he frequently promotes that of the society more effectually than when he really intends to promote it. I have never known much good done by those who affected to trade for the public good. It is an affectation, indeed, not very common among merchants, and very few words need be employed in dissuading them from it.

■ Source 4: Chapter 2 of Economics by Samuelson and Nordhaus

Every individual endeavors to employ his capital so that its produce may be of greatest value. He generally neither intends to promote the public interest, nor knows how much he is promoting it. He intends only his own security, only his own gain. And he is in this led by an invisible hand to promote an end which was no part of his intention. By pursuing his own interest he frequently promotes that of society more effectively than when he really intends to promote it. (quoted in Samuelson and Nordhaus's Economics on p. 25) 

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※ The final quote in the source 4 as reproduced in view of  the source 3:

(...) As every individual, therefore, endeavours as much as he can both to employ his capital in the support of domestic industry, and so to direct that industry that its produce may be of the greatest value; every individual necessarily labours to render the annual revenue of the society as great as he can. He generally, indeed, neither intends to promote the public interest, nor knows how much he is promoting it. By preferring the support of domestic to that of foreign industry, he intends only his own security; and by directing that industry in such a manner as its produce may be of the greatest value, he intends only his own gain, and he is in this, as in many other cases, led by an invisible hand to promote an end which was no part of his intention. Nor is it always the worse for the society that it was no part of it. By pursuing his own interest he frequently promotes that of the society more effectually than when he really intends to promote it.(...)

※ This part, “..., and he is in this, as in other cases, led by an invisible hand to promote an end which was no part of his intention” , may be paraphrased as following:

“..., and he is in this case, as in other ones, led by an invisible hand to promote ...”