What the buyer of an ordinary commodity buys is its use-value; what he pays for is its value. What the borrower of money buys is likewise its use-value as capital; but what does he pay for? Surely not its price, or value, as in the case of ordinary commodities. No change of form occurs in the value passing between borrower and lender, as occurs between buyer and seller when it exists in one instance in the form of money, and in another in the form of a commodity. The sameness of the alienated and returned value is revealed here in an entirely different way. The sum of value, i.e., the money, is given away without an equivalent, and is returned after a certain period. The lender always remains the owner of the same value, even after it passes from his hands into those of the borrower. In an ordinary exchange of commodities money always comes from the buyer's side; but in a loan it comes from the side of the seller. He is the one who gives away money for a certain period, and the buyer of capital is the one who receives it as a commodity. But this is only possible as long as the money acts as capital and is therefore advanced. The borrower borrows money as capital, as a value producing more value. But at the moment when it is advanced it is still only potential capital, like any other capital at its starting-point, the moment it is advanced. It is only through its employment that it expands its value and realises itself as capital. However, it has to be returned by the borrower as realised capital, hence as value plus surplus-value (interest). And the latter can only be a portion of the realised profit. Only a portion, not all of it. For the use-value of the loaned capital to the borrower consists in producing profit for him. Otherwise there would not have been any alienation of use-value on the lender's part. On the other hand, not all the profit can fall to the borrower's share. Otherwise he would pay nothing for the alienated use-value, and would return the advanced money to the lender as ordinary money, not as capital, as realised capital, for it is realised capital only as M + ΔM.