As use-values, commodities differ above all in quality, while as exchange-values they can only differ in quantity, and therefore do not contain an atom of use-value.

As exchange-values, all commodities are merely definite quantities of congealed labour-time.

A use-value, or useful article, therefore, has value only because abstract human labour is objectified or materialized in it. How, then, is the magnitude of this value to be measured? By means of the quantity of the "value-forming substance", the labour, contained in the article. This quantity is measured by its duration, and the labour-time is itself measured on the particular scale of hours, days etc.

A use-value, or useful article, therefore, has value only because abstract human labour is objectified or materialized in it. How, then, is the magnitude of value to be measured? By means of the quantity of the "value-forming substance", the labour, contained in the article. This quantity is measured by its duration, and the labour-time is itself measured on the particular scale of hours, days etc.

What exclusively determines the magnitude of the value of any article is therefore the amount of labour socially necessary, or the labour-time socially necessary for its production.

This false appearance distinguishes wages labour from other historical forms of labour. On the basis of the wages system even the unpaid labour seems to be paid labour. With the slave, on the contrary, even that part of his labour which is paid appears to be unpaid. Of course, in order to work the slave must live, and one part of his working day goes to replace the value of his own maintenance. But since no bargain is struck between him and his master, and no acts of selling and buying are going on between the two parties, all his labour seems to be given away for nothing.