Smith begins by setting out the source of a commodity's value. He states,

"Every man is rich or poor according to the degree in which he can afford to enjoy the necessaries, conveniencies, and amusements of human life. But after the division of labour has once thoroughly taken place, it is but a very small part of these with which a man's own labour can supply him. The far greater part of them he must derive from the labour of other people, and he must be rich or poor according to the quantity of that labour which he can command, or which he can afford to purchase. The value of any commodity, therefore, to the person who possesses it, and who means not to use or consume it himself, but to exchange it for other commodities, is equal to the quantity of labour which it enables him to purchase or command. Labour, therefore, is the real measure of the exchangeable value of all commodities. The real price of every thing, what every thing really costs to the man who wants to acquire it, is the toil and trouble of acquiring it."^[2]

This is known as the labour theory of value, a defining feature of classical political economy. Smith then distinguishes between the nominal value of a commodity (in money denomination) and its real value in the labour required to purchase it. According to Smith, while the nominal value of a commodity is subject to fluctuation, this does not change its real value, because the amount of labour required to produce it and bring it to the market remains constant.

For example, the price of a commodity redeemable in silver may be 1:1, as the amount of labour required to produce that commodity is the same as the amount of labour required to retrieve one piece of silver. However, with the discovery of new silver mines in North America, a surge in the supply of silver in the economy may bring the nominal price of the commodity in silver to 1:2. Yet this does not affect the commodity's real value, because the abundance of silver in the newly discovered mines does not suppose a lesser degree of labour required to retrieve them, but simply a greater availability of silver in the market. It is this greater availability that accounts for the deflation of the price; while the commodity is worth just as much labour now as it was before, it will not command as much power in the economy as before. However, if the price were to rise to 1:2 as a result of technological improvements in the manufacture or transport of the commodity, this would constitute a decline in its real value, because less labour is necessary to produce and market it.