Now, while by adapting capital in proper forms we may increase the effective power of labor to impress upon matter the character of wealth, as when we adapt wood and iron to the form and use of a plane; or iron, coal, water, and oil to the form and use of a steam engine; or stone, clay, timber, and iron to that of a building, yet the characteristic of this use of capital is, that the benefit is in the use. When, however, we employ capital in the second of these modes, as when we plant grain in the ground, or place animals on a stock farm, or put away wine to improve with age, the benefit arises, not from the use, but from the increase. And so, when we employ capital in the third of these modes, and instead of using a thing we exchange it, the benefit is in the increase or greater value of the things received in return. Primarily, the benefits which arise from use go to labor, and the benefits which arise from increase, to capital. But, inasmuch as the division of labor and the interchangeability of wealth necessitate and imply an averaging of benefits, in so far as these different modes of production correlate with each other, the benefits that arise from one will average with the benefits that arise from the others, for neither labor nor capital will be devoted to any mode of production while any other mode which is open to them will yield a greater return. That is to say, labor expended in the first mode of production will get, not the whole return, but the return minus such part as is necessary to give to capital such an increase as it could have secured in the other modes of production, and capital engaged in the second and third modes will obtain, not the whole increase, but the increase minus what is sufficient to give to labor such reward as it could have secured if expended in the first mode. Thus interest springs from the power of increase which the reproductive forces of nature, and the in effect analogous capacity for exchange, give to capital. It is not an arbitrary, but a natural thing; it is not the result of a particular social organization, but of laws of the universe which underlie society. It is, therefore, just.