These remarks, it must be allowed, are justly applicable to those who propose to measure the values of commodities by the quantity of labour actually bestowed upon them; but in no degree to those who propose to measure them by the quantity of labour which they will command. We have already shown that the labour which commodities will command measures that paramount cause of value which includes every other; namely, the state of the supply as compared with the demand. Whatever may be the number and variety of considerations operating on the mind in the interchange of commodities, whether merely the common elementary costs of production, or whether these costs have been variously modified by taxes, by portions of rent, by monopolies strict or partial, and by temporary scarcity or abundance, the result of the whole must appear in the state of the supply compared with the demand; and in the case of an individual article, the supply of which may be considered as given, the demand, must be proportioned to the sacrifice which the purchasers are able and, under all the circumstances, willing to make in order to attain it. But it has already been shown that it is the command of labour which the purchasers are able and willing to transfer to the sellers, and not any particular commodity, except in proportion as it will command labour, that can alone represent the sacrifice of the purchasers. The labour, therefore, which a commodity will command, or which the purchasers are willing to give for it, measures the result of all the causes of value acting upon it,—of all the various considerations operating upon the mind in the interchange of commodities. Whether then we consider the value of a commodity at any place and time as expressed by the estimation in which it is held; whether we consider it as founded entirely on the state of the supply as compared with the demand; whether we consider it as determined by the sacrifice which people are willing to make in order to obtain it; or by the natural and necessary conditions of its supply; or by the elementary costs of its production; or by the number of its producers; or by the result of all the causes of value operating upon it, it is plain that the labour which it will ordinarily command in any place will measure its natural and ordinary value; and the labour which it will actually command will measure its market value.