We have defined value at great length and with various illustrations, with the result, to our minds, that it arises from the union of desire and labor; but we have not defined the latter term.

What is labor?

The voluntary efforts of human beings to produce objects of desire.

Labor is always irksome. This is law. Men do not voluntarily put forth their exertions, except for a reward. By the beneficent provision of Nature, habit assists our activities ; great desires overcome the sense of weariness and pain ; the impetus of one movement carries us on into the next. Toil has its compensations. Its fruit is pleasant and wholesome. But not the less is it, of itself, against the drift of man's natural inclinations.* It is because men do not voluntarily put forth exertions, except for a reward, that every thing which costs labor will, as a general rule, command a corresponding amount of service or labor. Therefore it is that labor is the essential measure of value. Whatever disturbing causes there may be, it will, on the whole and in the long-run, be true that labor commands its equivalent in labor.

* " Labor is either bodily or mental, or, to express the distinction more comprehensively, either muscular or nervous ; and it is necessary to include in the idea, not solely the exertion itself, but all feelings of a disagreeable kind, all bodily inconvenience or mental annoyance, connected with the employment of one's thoughts or muscles, or both, in a particular occupation.' — J. Stuart Mill, Principles of Political Economy, p. 29, Am. ed., vol. i.

In this definition, we have spoken of voluntary efforts alone, because involuntary or uncompensated efforts are not to be classed as labor. They are merely the result of the use of a given amount of capital. Slaves are owned, like horses or oxen; and what value they confer is from their employment as so much capital. This distinction is not unimportant, because we shall see that capital is controlled by other laws than those which govern labor.

Under a free-labor system, as will be shown, there are two proprietors of value,—the laborer and the capitalist. Under a slave-labor system, only the latter has any share in the product.