The introduction of money does not interfere with the operation of any of the Laws of Value.... The reasons which make the temporary or market value of things depend on the demand and supply, and their average and permanent values upon their cost of production, are as applicable to a money system as to a system of barter. Things which by barter would exchange for one another, will, if sold for money, sell for an equal amount of it, and so will exchange for one another still, though the process of exchanging them will consist of two operations instead of only one. The relations of commodities to one another remain unaltered by money: the only new relation introduced, is their relation to money itself; how much or how little money they will exchange for; in other words, how the Exchange Value of money itself is determined. And this is not a question of any difficulty, when the illusion is dispelled, which caused money to be looked upon as a peculiar thing, not governed by the same laws as other things. Money is a commodity, and its value is determined like that of other commodities, temporarily by demand and supply, permanently and on the average by cost of production. In the foregoing,[2] attention has been directed mainly to the two functions of money known (1) as the Standard or Common Denominator of Value, and (2) as the Medium of Exchange. Concerning transactions begun and ended on the spot nothing more need be said; but the fact of contracts over a period of time introduces an important element--the time element. Whenever a contract is made covering a period of time, within which serious changes in the economic world may take place, then difficulties may arise as to what is a just standard of payments. Various articles might serve equally well as a standard for exchanges performed on the spot, but it is not so when any one article is chosen as a standard for deferred payments. Without much regard to theory, the world has in fact used the same standard for transactions whether settled on the spot, or whether extending over a period of time.