7. Turning to social conditions, we meet the new problem of exchange value. It is true, certain value comparisons may be made in the entirely isolated economy which afford a kind of prototype of the exchange value of the market. Crusoe might, perhaps, have occasion to make mental note that ten bushels of his wheat supply possess the same esteem value to him as one cord of his firewood. This comparison involves a ratio between valuable goods, and if Crusoe only had reason to trade with himself we might find the phenomenon of purchasing power—the true conception of exchange value—and ten bushels of wheat would have the purchasing power of one cord of wood. This kind of exchange value—if we dare call it such—would be most simple; for it would be directly determined by, and be in exact proportion to, esteem value. Just as Crusoe will be able to carry the esteem values of reproducible goods in mind most readily in terms of disutility cost, so would he be able to strike value ratios between such goods most easily by comparing the disutility costs of their physical units of measure. Thus, if one cord of wood should exchange for ten bushels of wheat, the reason would be that a bushel of wheat costs one-tenth as much labor as one cord of wood. This thought need not be pursued further. If the exchange value of a good in the social market depended in the same direct manner upon the esteem value of that good to all society or to “society as a unit,” the final theory of exchange value would be much simplified. But, unless the present writer is mistaken, a good cannot possess an esteem value to society as a whole, but can merely have a separate value to each individual member of society.