4. But there is another element which is essential to value; this is _utility_. It comprises all those qualities in an object which make it available to gratify any desire. It will readily be seen that there are objects which have utility and at the same time are without value. They are such objects as cost nothing; that is, such as involve no labor in their acquisition. Thus air, and sunshine, and rain, have no value; but they are of immeasurable utility. Value is often in the inverse ratio of utility. Iron is a far more useful metal than gold, but gold is vastly more valuable than iron. Still, though utility may exist where there is no value, there can be no value where there is no utility; because no one would put forth effort for that which could not gratify any desire, and it is the ability to gratify desire that constitutes utility. Sometimes utility becomes the paramount element in determining value; but ordinarily it is subordinate to the cost of production. When the article is one for which there is a very great demand, and of which there is a great scarcity, the value may increase many times beyond the cost. In such case the utility rather than cost rules. But where the demand is readily and fully met by the supply, the cost controls. 5. But valuable things can not be produced very largely without tools, implements, and various contrivances. These constitute _capital_. _Capital is the result of previous labor reserved and employed in further production._ This implies self-denial. A man can not consume what he has secured by labor and at the same time preserve it to aid in additional production. Hence he must restrain his desires if he would save something for this purpose. This capital is sometimes called pre-existent labor. The point to be observed is that its existence is due, not to labor alone, but to _abstinence_ as well. The two elements in the cost of production are labor and abstinence, and we may combine these in the one term, _sacrifice_. Sacrifice and utility, then, are the two essential conditions of value; and we may complete our definition of value by saying that _value is man’s estimate of the amount of sacrifice requisite to the attainment of a desired object_.