The difference in increasableness of the various forms of wealth is of importance in considering various social questions such as the effects of an increase of population, and the kinds of taxation most equitable and most favorable to the progress of society. Account must be taken of the fact that the number of bricks can be increased more easily than the amount of land; but there must not be overlooked the possibility of increase in any of these forms of wealth, nor the limits to the increase of any one of them. When one wishes to save or increase wealth, he turns to these great unappropriated fields, unused things or things imperfectly used, and tries to convert them into effective agents. The different forms of wealth may be ranged on a scale according to the ease with which they can be increased by effort. They may therefore be classed as relatively fixed and relatively increasable. Some natural resources belong at one end, and some at the other end of this scale. No hard and fast line divides the different kinds of goods, but the difference in degree of increasableness is a fact of great social importance, affecting the direction in which industry can and must progress. CHAPTER 19 SAVING AND PRODUCTION AS AFFECTED BY THE RATE OF INTEREST § I. SAVING AS AFFECTED BY THE INTEREST RATE [Sidenote: The interest rate traces the division between present and future gratifications] 1. _In the case of consumption goods, present marginal uses are often less than future uses as judged at the present._ The proposition that future goods sometimes have a greater instead of a less value than present goods may at first seem to deny the general fact of economic interest, which is a premium on present over future goods. The contradiction is only apparent, however, and the proposition is merely a proper interpretation of the theory of interest. The assertion that present goods have greater value than future goods, as we have accepted it, requires two explanations. First, it means that this difference exists when the two are judged and compared _at the present moment_. The future use when it matures may be much greater than the present use; indeed, the very existence of interest depends upon this surplus of value arising by the lapse of time in the future use. Secondly, the proposition does not mean that every concrete good, or every use of the goods, is worth more in the present than in the future; it means merely that the demand for present goods preponderates so that a market rate in favor of present possession prevails. In a great many cases a particular good may have a greater value to be kept for the future than to be used at present, in which case it is kept, or it is exchanged for something else having a higher value in the present. But this preference of the future over the present cannot pass a moderate limit without condemning the person to present misery, and at length to death. On the other hand