4. _The rate of capitalization of income and the rate of contract interest on money capital tend to unite into a single market rate._ A person wishing to exchange present goods or income for future goods may buy an income-bearer at its capitalized value, or he may create a new rent-bearer. Having saved a sum of money, either he may purchase a factory known to be profitable; or he may hire the services of men and unite them with materials and machinery to create a new industry or a new form of income-bearer; or he may loan his money to others to make either kind of purchase. In any one of the three cases it is evident that capitalization (that is, the discounting of future rents in goods) is the primary and important fact making possible the emergence of a surplus, or net yield, over and above the value of the capital. The expected uses contained not only in whole industrial establishments, but in the particular materials and agents united to form new agents, are purchased at their capitalized value; that is, the future uses have been discounted and have entered into the price of the goods as less than they will be when realized as actual rents. This is the crucial point in the theory either of contract interest or of time value; for to explain the rate of interest as due to the process of "producing" capital agents out of other materials, is to beg the question involved. The surplus yielded by capital above its cost is but the realization of a net income made possible by the discounting of future rents. [Sidenote: The choice open to the borrower of wealth]