The soil without the labourers would produce no loaves at all.

The labourers would produce no loaves if they had not the soil to work upon.
Now, if there were only one farm in the world, and one grade of labour, and if every acre of this farm, when the same labour was applied to it, would always yield the same amount of produce--let us say one loaf--Mill's argument would be true.

The actual state of the case is, however, very different.

Acres vary very greatly in quality; and if we take four acres of varying degrees of fertility, to all of which is applied the same amount of labour, then, while from the worst of the acres this labour will elicit one loaf, it will elicit from the others, let us say, according to their degrees of fertility, two loaves, three loaves, and four loaves respectively.

Here the labour being in each of the four cases the same, and the additional loaves resulting in three cases only, it is obvious that the difference between the larger products and the less is not due to the labour, but to certain additional qualities present, in the three superior acres and not present in the worst one.