4. _Labor being of many qualities and receiving many rates of pay, there is no unit of labor that can be used as a measure of value._ The idea of finding in a "unit of labor" an objective standard of value to which the value of all other things could be reduced has been a very attractive one. This fallacious hope animates every one beginning to think of the value problem. The thought was so plausibly formulated by Ricardo that it continued for a long time to be the generally accepted doctrine of value. Although most writers reject the formal statement of the labor theory of value, use is frequently made, even now, of the phrase "unit of labor," suggesting the thought that labor is the standard by which the value of all goods may be measured. This unit of labor of the text-books may be seen to be either labor arbitrarily assumed to be of uniform quality and quantity, as a day of unskilled labor (in that form quite incomparable as to amount with other qualities), or a given amount of money invested in labor of different grades at its market value. It is only by expressing labor in terms of its value that the various grades of skilled and unskilled labor can be reduced to a homogeneous unit, which is but a unit of money wages. This should not deceive us into the belief that in any peculiar sense labor can be used as a unit of value. It is equally valid and convenient to speak of units of machinery and of units of land. In terms of capital a factory site can be expressed as a multiple of a potato patch not less perfectly than can a sculptor's labor as a multiple of a ditch-digger's. [Sidenote: Scarcity and utility of labor] Scarcity of things desired is the one objective condition of value. The things that labor can produce and the labor to produce them being scarce, labor takes on a value. All things at last become comparable in terms of psychic income in each individual's judgment, but as yet neither in this comparison nor in the market values that are fixed in exchange, has any absolute standard been found by which the utility of all goods or the welfare of all men can be measured. CHAPTER 25 THE WAGE SYSTEM AND ITS RESULTS § I. SYSTEMS OF LABOR [Sidenote: The wage system defined] [Sidenote: Never the exclusive form of organization]