But, the more men become used to comparing the aggregate of human wants, and the aggregate of the goods which minister to the satisfaction of these wants, as if they were two great wholes, gradually shading each into the other, the more does the value in use of the different kinds of goods assume, for purposes of social rating or estimation, a fungible character.(76) If a new kind of goods be produced or discovered, which satisfies the same wants in a more complete manner than another, the latter, although it has suffered no change, generally loses in the value put upon it, especially if the new goods can be produced in any desired quantity. An instance of this is the change effected in the value of the dyers weed, woad, by the introduction of indigo. Things present in quantities greater than the amount necessary to supply the want they satisfy, preserve their full value in use, to the limit of that want, after which they are simply an element of possible future value, dependent on an increase of the want; but they have no value for present use.(77) The economic valuation of goods, however, is by no means exhausted, so far as the isolated individual housekeeper is concerned, by the mere establishing of its value in use. As the systematic effort of every rational individual in his household management is directed towards the obtaining, by a minimum of sacrifice of pleasure and energy, a maximum satisfaction of his wants, even an Adam or a Crusoe is, in his economy, compelled to estimate not only what the goods to be acquired accomplish (value in use) but also what they will cost—cost-value. Even the most indispensable kind of goods, for instance atmospheric air, is considered to have no value, when it can be obtained in sufficient quantity, without any sacrifice whatever.(78) Section V. Value.—Value In Exchange. The value in exchange of goods, or the quality which makes them exchangeable against other goods, is based on a combination of their value in use with their cost-value, such as men in their intercourse with one another will make.(79) Without value in use, value in exchange(80) is unthinkable. But there are many, and even indispensable goods which are not at all susceptible of being exchanged; for instance, the light and heat of the sun, the open sea etc.(81) Other goods, although capable of being exchanged, have no value in exchange, because they exist in superabundance, and may be obtained by everyone, without trouble and without reward; for instance, drinking-water in most places, ice in winter, and wood in the primeval forest.(82) Moreover, the idea of such “free goods” is in great part relative. The water of a river may, for drinking purposes, be “free” goods, and yet, for purposes of irrigation, have great value in exchange. (_John Stuart Mill_).