From what has just been said we may conclude that the price of any good is determined by the demand for, and the supply of, that particular good. Generally speaking, such is the case; but a few modifications in the statement will lead to a more definite understanding. Demand is used here as nothing more or less than the willingness and the ability of those who desire to possess the good, to pay the market price. Supply, as we have just seen, may mean one of several things. In this case it means the quantity of the particular good offered for sale, and does not include, as many think, the whole amount of such good in existence. In other words, the price is set not by desires for any good on the one hand, and the total supply of that good on the other; but by demand (effective desire) and the volume freely offered to fill this demand.