as preserving pretty nearly its real value in exchange at different periods.”[130] In his correspondence with Malthus, Ricardo made the former very uncomfortable in the position taken with respect to the combined labor-corn measure of value. In the second edition of the _Principles_ of Malthus this hybrid standard was abandoned. In principle it was a shallow makeshift. It is needless to say that if the arguments for regarding the amount of commodities purchaseable by a day’s wages, as the unit of wealth, are sufficient, grain should be measured in its “real value” by reference to this standard in the same way as any other important commodity. As was stated in Chapter ii, the corn measure of value was suggested by Smith to serve as a convenient index to the labor measure. Beyond a doubt, Smith spoke of the corn measure in a way to mislead both Ricardo and Malthus; but nothing could be plainer than the words quoted from him to show that corn is used on principle only because it is supposed to remain from age to age in a steady exchange ratio with day labor.[131] In Malthus’s second edition, the view is taken simply that “standard” labor commanded in exchange is the measure of value in all times and places. There is great difficulty in telling precisely what value, or what kind of value, it is that is measured. It is called “real value in exchange” and “intrinsic value in exchange.” The latter is in one place defined to be “not the general power of purchasing possessed by a particular commodity, but its power of purchasing _arising from intrinsic causes_, which includes all the causes of whatever kind they may be, which have contributed to the limitation of its supply compared with the demand.”[132] The extrinsic causes of a commodity’s exchange value are the causes of the value of the other commodity in whose quantity the exchange value of the first is expressed.[133] In various other places, “intrinsic value in exchange” is defined as indicating (1) the degree of necessity or convenience to life (1st ed.); (2) the difficulty of obtainment (in some sense supposed to be more inclusive than Ricardo’s labor cost); (3) the degree of the limitation of the supply as compared with the demand. Thinking with such terminology would be like painting portraits with a white-wash brush. If a day of labor in America commanded twice the physical quantity of a given complex of commodities that a day of English labor commanded, Malthus was forced to admit that the simple exchange value of the goods commanded by a unit of American labor was twice that commanded by a unit of British labor. But at the same time his doctrine of the labor measure of value required him to affirm that the “real exchange value” of the goods commanded by a day of labor in the two countries was the same. In this way he was led to contend that two complexes of goods having different exchange values, had the same “real exchange values.” In view of the fact that “real exchange value”