(2) The labour in general it will purchase. (3) The labour necessary to produce more of it. The first kind of labour in no way affects the existing supply or demand of the commodity, and is neither a measure of its value nor a regulator or determining factor of such value. Evidences are not lacking to prove that a commodity will frequently not exchange for as much labour as was expended in producing it. The second kind of labour, the amount in general which a commodity will purchase, depends on the amount of commodities such labour will produce, less the share which goes to capital as its reward; for, neglecting rent or classing it with capital, these two, labour and capital, are joint factors in production and divide between them the total product. It is hardly necessary to observe that labour is continually growing more efficient; that improved skill and methods enable a much larger amount of commodities in general to be produced, with a certain amount of labour, than could formerly be produced; and that labour receives, as its share of such product, a much larger amount than formerly. It is thus evident, that a commodity which would exchange for the same amount of labour now as formerly, would exchange for a much larger amount of commodities in general now than then, and, if we adhere to our definition of exchange value, would be worth _more_ than formerly; while if labour be taken as a standard of value, it would be worth the _same_. The use of this form of labour as a standard of value is, it will be seen, incompatible with the definition of value. It may serve as a measure of the relative values of two commodities at any particular time and place, just as any third commodity may; but, as Ricardo remarks, "is subject to as many fluctuations as the commodities compared with it." The same argument applies to the third form of labour--that necessary to produce more of a commodity. This form of labour, however, is one of the factors in the cost of production, and through its effect on cost is one of the more remote factors that determine value, as explained in considering cost of production, but this does not make it in any sense a standard. We may conclude, then, that labour in any form is not a standard of value; that, as John Stuart Mill observes, it "discards the idea of exchange value altogether, substituting a totally different idea, more analogous to value in use."