 In our first discussion of the general, or average, rate of profit (Part II of this book) we did not have this rate before us in its complete form, the equalisation of profit appearing only as equalisation between industrial capitals invested in different spheres. This was supplemented in the preceding part, which dealt with the participation of merchant's capital in this equalisation, and also commercial profit. The general rate of profit and the average profit now appeared in narrower limits than before. It should be remembered in the course of our analysis that in any future reference to the general rate of profit or to average profit we mean this latter connotation, hence only the final form of average rate. And since this rate is the same for mercantile, as well as industrial, capital, it is no longer necessary, so far as this average profit is concerned, to make a distinction between industrial and commercial profit. Whether industrially invested in the sphere of production, or commercially in the sphere of circulation, capital yields the same average annual profit pro rata to its magnitude. Money here taken as the independent expression of a certain amount of value existing either actually as money or as commodities may be converted into capital on the basis of capitalist production, and may thereby be transformed from a given value to a self-expanding, or increasing, value. It produces profit, i.e., it enables the capitalist to extract a certain quantity of unpaid labour, surplus-product and surplus-value from the labourers, and to appropriate it. In this way, aside from its use-value as money, it acquires an additional use-value, namely that of serving as capital. Its use-value then consists precisely in the profit it produces when converted into capital. In this capacity of potential capital, as a means of producing profit, it becomes a commodity, but a commodity sui generis. Or, what amounts to the same, capital as capital becomes a commodity. Suppose the annual average rate of profit is 20%. In that case a machine valued at 100, employed as capital under average conditions and an average amount of intelligence and purposive effort, would yield a profit of 20. A man in possession of 100, therefore, possesses the power to make 120 out of 100, or to produce a profit of 20. He possesses a potential capital of 100. If he gives these 100 to another for one year, so the latter may use them as real capital, he gives him the power to produce a profit of 20 a surplus-value which costs this other nothing, and for which he pays no equivalent. If this other should pay, say, 5 at the close of the year to the owner of the 100 out of the profit produced, he would thereby pay the use-value of the 100 the use-value of its function as capital, the function of producing a profit of 20. The part of the profit paid to the owner is called interest, which is just another name, or special term, for a part of the profit given up by capital in the process of functioning to the owner of the capital, instead of putting it into its own pocket. It is plain that the possession of 100 gives their owner the power to pocket the interest that certain portion of profit produced by means of his capital. If he had not given the 100 to the other person, the latter could not have produced any profit, and could not at all have acted as a capitalist with reference to these 100.  To speak here of natural justice, as Gilbart does (see note), is nonsense. The justice of the transactions between agents of production rests on the fact that these arise as natural consequences out of the production relationships. The juristic forms in which these economic transactions appear as wilful acts of the parties concerned, as expressions of their common will and as contracts that may be enforced by law against some individual party, cannot, being mere forms, determine this content. They merely express it. This content is just whenever it corresponds, is appropriate, to the mode of production. It is unjust whenever it contradicts that mode. Slavery on the basis of capitalist production is unjust; likewise fraud in the quality of commodities. The 100 produce the profit of 20 because they function as capital, be it industrial or mercantile. But the sine qua non of this function as capital is that they are expended as capital, i.e., are expended in purchasing means of production (in the case of industrial capital) or commodities (in the case of merchant's capital). But to be expended, they must be available. If A, the owner of the 100, were either to spend them for personal consumption, or to keep them as a hoard, they could not have been invested as capital by B in his capacity of functioning capitalist. B does not expend his own capital, but A's; however, he cannot expend A's capital without A's consent. Therefore, it is really A who originally expends the 100 as capital, albeit his function as capitalist is limited to this outlay of 100 as capital. In respect to these 100, B acts as capitalist only because A lends him the 100, thus expending them as capital. Let us first consider the singular circulation of interest-bearing capital. We shall then secondly have to analyse the peculiar manner in which it is sold as a commodity, namely loaned instead of relinquished once and for all. The point of departure is the money which A advances to B. This may be done with or without security. The first-named form, however, is the more ancient, save advances on commodities or paper, such as bills of exchange, shares, etc. These special forms do not concern us at this point. We are dealing here with interest-bearing capital in its usual form. In B's possession the money is actually converted into capital, passes through M C M' and returns to A as M', as M+ M, where M represents the interest. For the sake of simplicity we shall not consider here the case, in which capital remains in B's possession for a long term and interest is paid at regular intervals. The movement, therefore, is M M C M' M'. What appears duplicated here, is 1) the outlay of money as capital, and 2) its reflux as realised capital, as M' or M+ M. In the movement of merchant's capital, M C M', the same commodity changes hands twice, or more than twice, if merchant sells to merchant. But every such change of place of the same commodity indicates a metamorphosis, a purchase or sale of the commodity, no matter how often the process may be repeated, until it enters consumption. On the other hand, the same money changes hands twice in C M C, but this indicates the complete metamorphosis of the commodity, which is first converted into money and then from money back into another commodity. But in interest-bearing capital the first time M changes hands is by no means a phase either of the commodity metamorphosis, or of reproduction of capital. It first becomes one when it is expended a second time, in the hands of the active capitalist who carries on trade with it, or transforms it into productive capital. M's first change of hands does not express anything here, beyond its transfer from A to B a transfer which usually takes place under certain legal forms and stipulations. This double outlay of money as capital, of which the first is merely a transfer from A to B, is matched by its double reflux. As M', or M + M, it flows back out of the process to B, the person acting as capitalist. The latter then transfers it back to A, but together with a part of the profit, as realised capital, as M + M, in which M is not the entire profit, but only a portion of the profit the interest. It flows back to B only as what he had expended, as functioning capital, but as the property of A. To make its reflux complete, B must consequently return it to A. But in addition to the capital, B must also turn over to A a portion of the profit, a part which goes under the name of interest, which he had made with this capital since A had given him the money only as a capital, i.e., as value which is not only preserved in its movement, but also creates surplus-value for its owner. It remains in B's hands only so long as it is functioning capital. And with its reflux on the stipulated date it ceases to function as capital. When no longer acting as capital, however, it must again be returned to A, who had never ceased being its legal owner. The form of lending, which is peculiar to this commodity, to capital as commodity, and which also occurs in other transactions instead of that of sale, follows from the simple definition that capital obtains here as a commodity, or that money as capital becomes a commodity. A distinction should be made here. We have seen (Book II, Chap. I), and recall briefly at this point, that in the process of circulation capital serves as commodity-capital and money-capital. But in neither form does capital become a commodity as capital. As soon as productive capital turns into commodity-capital it must be placed on the market to be sold as a commodity. There it acts simply as a commodity. The capitalist then appears only as the seller of commodities, just as the buyer is only the buyer of commodities. As a commodity the product must realise its value, must assume its transmuted form of money, in the process of circulation by its sale. It is also quite immaterial for this reason, whether this commodity is bought by a consumer as a necessity of life, or by a capitalist as means of production, i.e., as a component part of his capital. In the act of circulation commodity-capital acts only as a commodity, not as a capital. It is commodity-capital, as distinct from an ordinary commodity, 1) because it is weighted with surplus-value, the realisation of its value, therefore, being simultaneously the realisation of surplus-value; but this alters nothing about its simple existence as a commodity, as a product with a certain price; 2) because its function as a commodity is a phase in its process of reproduction as capital, and therefore its movement as a commodity being only a partial movement of its process, is simultaneously its movement as capital. Yet it does not become that through the sale as such, but only through the connection of the sale with the whole movement of this specific quantity of value in the capacity of capital. In the same way as money-capital it really acts simply as money, i.e., as a means of buying commodities (the elements of production). The fact that this money is simultaneously money-capital, a form of capital, does not emerge from the act of buying, the actual function which it here performs as money, but from the connection of this act with the total movement of capital, since this act, performed by capital as money, initiates the capitalist production process. But in so far as they actually function, i.e., actually play a role in the process, commodity-capital acts here only as a commodity and money-capital only as money. At no time during the metamorphosis, viewed by itself, does the capitalist sell his commodities as capital to the buyer, although to him they represent capital; nor does he give up money as capital to the seller. In both cases be gives up his commodities simply as commodities, and money simply as money, i.e., as a means of purchasing commodities. It is only in connection with the entire process, at the moment where the point of departure appears simultaneously as the point of return, in M M' or C C', that capital in the process of circulation appears as capital (whereas in the process of production it appears as capital through the subordination of the labourer to the capitalist and the production of surplus value). In this moment of return, however, the connection disappears. What we have then is M', or M + M, a sum of money equal to the sum originally advanced plus an increment the realised surplus-value (regardless of whether the amount of value increased by M exists in the form of money, or commodities, or elements of production). And it is precisely at this point of return where capital exists as realised capital, as an expanded value, that it never enters the circulation in this form in so far as this point is fixed as a point of rest, whether real or imaginary but rather appears to have been withdrawn from circulation as a result of the whole process. Whenever it is again expended, it is never given up to another as capital, but is sold to him as an ordinary commodity, or given to him as ordinary money in exchange for commodities. It never appears as capital in its process of circulation, only as commodity or money, and at this point this is the only form of its existence for others. Commodities and money are here capital not because commodities change into money, or money into commodities, not in their actual relations to sellers or buyers, but only in their ideal relations to the capitalist himself (subjectively speaking), or as phases in the process of reproduction (objectively speaking). Capital exists as capital in actual movement, not in the process of circulation, but only in the process of production, in the process by which labour-power is exploited. The matter is different with interest-bearing capital, however, and it is precisely this difference which lends it its specific character. The owner of money who desires to enhance his money as interest-bearing capital, turns it over to a third person, throws it into circulation, turns it into a commodity as capital; not just capital for himself, but also for others. It is not capital merely for the man who gives it up, but is from the very first given to the third person as capital, as a value endowed with the use-value of creating surplus-value, of creating profit; a value which preserves itself in its movement and returns to its original owner, in this case the owner of money, after performing its function. Hence it leaves him only for a specified time, passes but temporarily out of the possession of its owner into the possession of a functioning capitalist, is therefore neither given up in payment nor sold, but merely loaned, merely relinquished with the understanding that, first, it shall return to its point of departure after a definite time interval, and, second, that it shall return as realised capital a capital having realised its use-value, its power of creating surplus-value. Commodities loaned out as capital are loaned either as fixed or as circulating capital, depending on their properties. Money may be loaned out in either form. It may be loaned as fixed capital, for instance, if it is paid back in the form of an annuity, whereby a portion of the capital flows back together with the interest. Certain commodities, such as houses, ships, machines, etc., can be loaned out only as fixed capital by the nature of their use-values. Yet all loaned capital, whatever its form, and no matter how the nature of its use-value may modify its return, is always only a specific form of money-capital. Because what is loaned out is always a definite sum of money, and it is this sum on which interest is calculated. Should whatever is loaned out be neither money nor circulating capital, it is also paid back in the way fixed capital returns. The lender periodically receives interest and a portion of the consumed value of the fixed capital itself, this being an equivalent for the periodic wear and tear. And at the end of the stipulated term the unconsumed portion of the loaned fixed capital is returned in kind. If the loaned capital is circulating capital, it is likewise returned in the manner peculiar to circulating capital. The manner of reflux is, therefore, always determined by the actual circuit described by capital in the act of reproduction and by its specific varieties. But as for loaned capital, its reflux assumes the form of return payments, because its advance, by which it is transferred, possesses the form of a loan. In this chapter we treat only of actual money-capital, from which the other forms of loaned capital are derived. The loaned capital flows back in two ways. In the process of reproduction it returns to the functioning capitalist, and then its return repeats itself once more as transfer to the lender, the money-capitalist, as return payment to the real owner, its legal point of departure. In the actual process of circulation, capital appears always as a commodity or as money, and its movement always is broken up into a series of purchases and sales. In short, the process of circulation resolves itself into the metamorphosis of commodities. It is different, when we consider the process of reproduction as a whole. If we start out with money (and the same is true if we start out with commodities, since we begin with their value, hence view them sub specie as money), we shall see that a certain sum of money is expended and returns after a certain period with an increment. The advanced sum of money returns together with a surplus-value. It has remained intact and increased in making a certain cycle. But now, being loaned out as capital, money is loaned as just the sum of money which preserves and expands itself, which returns after a certain period with an increment, and is always ready to perform the same process over again. It is expended neither as money nor as a commodity, thus, neither exchanged against a commodity when advanced in the form of money, nor sold in exchange for money when advanced as a commodity; rather, it is expended as capital. This relation to itself, in which capital presents itself when the capitalist production process is viewed as a whole and as a single unity, and in which capital appears as money that begets money, is here imparted to it as its character, its designation, without any intermediary movement. And it is relinquished with this designation when loaned out as money-capital. A queer conception of the role of money-capital is hold by Proudhon (Gratuit du Cr dit. Discussion entre M. F. Bastiat et M. Proudhon, Paris, 1850). Loaning seems an evil to Proudhon because it is not selling. Loaning for an interest is The object money, a house, etc. does not change owners as in selling and buying. But Proudhon does not see that no equivalent is received in return for money given away in the form of interest-bearing capital. True, the object is given away in every act of buying and selling, so far as there are processes of exchange at all. Ownership of the sold article is always relinquished. But its value is not given up. In a sale the commodity is given away, but not its value, which is returned in the form of money, or in what is here just another form of it promissory notes, or titles of payment. When purchasing, the money is given away, but not its value, which is replaced in the form of commodities. The industrial capitalist retains the same value in his hands throughout the process of reproduction (excluding surplus-value), but in different forms. Inasmuch as there is an exchange, i.e., an exchange of articles, there is no change in the value. The same capitalist always retains the same value. But so long as surplus-value is produced by the capitalist, there is no exchange. As soon as an exchange occurs, the surplus-value is already incorporated in the commodities. If we view the entire circuit made by capital, M C M', rather than individual acts of exchange, we shall see that a definite amount of value is continually advanced, and that this same amount plus surplus-value, or profit, is withdrawn from circulation. The actual acts of exchange do not, at any rate, reveal how this process is promoted. And it is precisely this process of M as capital, on which the interest of the money-lending capitalist rests, and from which it is derived. Here the hatter represents the productive capitalist as distinct from the loan capitalist. Proudhon has obviously failed to grasp the secret of how the productive capitalist can sell commodities at their value (equalisation through prices of production is here immaterial to his conception) and receive a profit over and above the capital he flings into exchange. Suppose the price of production of 100 hats = 115, and that this price of production happens to coincide with the value of the hats, which means that the capital producing the hats is of the same composition as the average social capital. Should the profit = 15%, the hatter makes a profit of 15 by selling his commodities at their value of 115. They cost him only 100. If he produced them with his own capital, he pockets the entire surplus of 15 but if with borrowed capital, he may have to give up 5 as interest. This alters nothing in the value of the hats, only in the distribution among different persons of the surplus-value already contained in this value. Since, therefore, the value of the hats is not affected by the payment of interest, it is nonsense on Proudhon's part to say: How little Proudhon understood the nature of capital is shown in the following statement, in which he describes the movement of capital in general as a movement peculiar to interest-bearing capital: What is it that still puzzles him in the peculiar movement of interest-bearing capital? The categories: buying, price, giving up articles, and the immediate form in which surplus-value appears here; in short, the phenomenon that capital as such has become a commodity, that selling, consequently, has turned into lending and price into a share of the profit. The return of capital to its point of departure is generally the characteristic movement of capital in its total circuit. This is by no means a feature of interest-bearing capital alone. What singles it out is rather the external form of its return without the intervention of any circuit. The loaning capitalist gives away his capital, transfers it to the industrial capitalist, without receiving any equivalent. His transfer is not an act belonging to the real circulation process of capital at all. It serves merely to introduce this circuit, which is effected by the industrial capitalist. This first change of position of money does not express any act of the metamorphosis neither buying nor selling. Ownership is not relinquished, because there is no exchange and no equivalent is received. The return of the money from the hands of the industrial capitalist to those of the loaning capitalist merely supplements the first act of giving away the capital. Advanced in the form of money, the capital again returns to the industrial capitalist through the circular process in the form of money. But since it did not belong to him when he invested it, it cannot belong to him on its return. Passing through the process of reproduction cannot by any means turn the capital into his property. He must therefore restore it to the lender. The first expenditure, which transfers the capital from the lender to the borrower, is a legal transaction which has nothing to do with the actual process of reproduction. It is merely a prelude to this process. The return payment, which again transfers the capital that has flowed back from the borrower to the lender is another legal transaction, a supplement of the first. One introduces the actual process, the other is an act supplementary to this process. Point of departure and point of return, the giving away and the recovery of the loaned capital, thus appear as arbitrary movements promoted by legal transactions, which take place before and after the actual movement of capital and have nothing to do with it as such. It would have been all the same as concerns this actual movement if the capital had from the first belonged to the industrial capitalist and had returned to him, therefore, as his own. In the first introductory act the lender gives his capital to the borrower. In the supplemental and closing act the borrower returns the capital to the lender. As concerns the transaction between these two and aside from the interest for the present as concerns the movement of the loaned capital between lender and borrower, therefore, the two acts (separated by a longer or shorter time interval, during which the actual reproduction process of the capital takes place) embrace the entire movement. And this movement, disposing on condition of returning, constitutes per se the movement of lending and borrowing, that specific form of conditionally alienating money or commodities. The characteristic movement of capital in general, the return of the money to the capitalist, i.e., the return of capital to its point of departure, assumes in the case of interest-bearing capital a wholly external appearance, separated from the actual movement, of which it is a form. A gives away his money not as money, but as capital. No transformation occurs in the capital. It merely changes hands. Its real transformation into capital does not take place until it is in the hands of B. But for A it becomes capital as soon as he gives it to B. The actual reflux of capital from the processes of production and circulation takes place only for B. But for A the reflux assumes the same form as the alienation. The capital returns from B to A. Giving away, i.e., loaning money for a certain time and receiving it back with interest (surplus-value) is the complete form of the movement peculiar to interest-bearing capital as such. The actual movement of loaned money as capital is an operation lying outside the transactions between lender and borrower. In these the intermediate act is obliterated, invisible, not directly included. A special sort of commodity, capital has its own peculiar mode of alienation. Neither does its return, therefore, express itself as the consequence and result, of some definite series of economic processes, but as the effect of a specific legal agreement between buyer and seller. The time of return depends on the progress of the process of reproduction; in the case of interest-bearing capital, its return as capital seems to depend on the mere agreement between lender and borrower. So that in regard to this transaction the return of capital no longer appears as a result arising out of the process of reproduction; it appears as if the loaned capital never lost the form of money. To be sure, these transactions are really determined by the actual reproductive returns. But this is not evident in the transaction itself. Nor is it by any means always the case in practice. If the actual return does not take place in due time, the borrower must look for other resources to meet his obligations vis- -vis the lender. The bare form of capital money expended as a certain sum, A, which returns as sum A + 1/x A after a given lapse of time without any other intermediate act save this lapse of time is only a meaningless form of the actual movement of capital. In the actual movement of capital its return is a phase in the process of circulation. The money is first converted into means of production; production transforms them into commodities; through sale of the commodities they are reconverted into money and return in this form into the hands of the capitalist who had originally advanced the capital in the form of money. But in the case of interest-bearing capital, the return, like alienation, is the result of a legal transaction between the owner of the capital and a second party. We see only the alienation and the return payment. Whatever passes in the interim is obliterated. But since money advanced as capital has the property of returning to the person who advanced it, to the one who expended it as capital, and since M C M' is the immanent form of the movement of capital, the owner of the money can, for this very reason, loan it out as capital, as something that has the property of returning to its point of departure, of preserving, and increasing, its value in the course of its movement. He gives it away as capital, because it returns to its point of departure after having been employed as capital, hence can be restored by the borrower after a certain period precisely because it has come back to him. Loaning money as capital its alienation on the condition of it being returned after a certain time-presupposes, therefore, that it will be actually employed as capital, and that it actually flows back to its starting-point. The real cycle made by money as capital is, therefore, the premise for the legal transaction by which the borrower must return the money to the lender. If the borrower does not use the money as capital, that is his own business. The lender loans it as capital, and as such it is supposed to perform the functions of capital, which include the circuit of money-capital until it returns to its starting-point in the form of money. The acts of circulation, M C and C M', in which a certain amount of value functions as money or commodities, are but intermediate processes, mere phases of the total movement. As capital, it performs the entire movement M M'. It is advanced as money or a sum of values in one form or another, and returns as a sum of values. The lender of money does not expend it in purchasing commodities, or, if this sum of values is in commodity-form, does not sell it for money. He advances it as capital, as M M', as a value, which returns to its point of departure after a certain term. He lends instead of buying or selling. This lending, therefore, is the appropriate form of alienating value as capital, instead of alienating it as money or commodities. It does not follow, however, that lending cannot also take the form of transactions which have nothing to do with the capitalist process of reproduction. We have so far only considered the movements of loaned capital between its owner and the industrial capitalist. Now we must inquire into interest. The lender expends his money as capital; the amount of value, which he relinquishes to another, is capital, and consequently returns to him. But the mere return of it would not be the reflux of the loaned sum of value as capital, but merely the return of a loaned sum of value. To return as capital, the advanced sum of value must not only be preserved in the movement but must also expand, must increase in value, i.e., must return with a surplus-value, as M + M, the latter being interest or a portion of the average profit, which does not remain in the hands of the operating capitalist, but falls to the share of the money-capitalist. The fact that the latter has relinquished it as capital implies that it must be restored to him as M + M. Later, we shall also have to turn our attention to the form in which interest is paid in the meantime at fixed intervals, but without the capital, whose return follows at the end of a lengthy period. What does the money-capitalist give to the borrower, the industrial capitalist? What does he really turn over to him? It is only this act of handing over money which changes lending money into alienation of money as capital, i.e., alienation of capital as a commodity. It is only by this act of alienating that capital is loaned by the money-lender as a commodity, or that the commodity at his disposal is given to another as capital. What is alienated in an ordinary sale? Not the value of the sold commodity, for this merely changes its form. The value exists ideally in a commodity as its price before it actually passes as money into the hands of the seller. The same value and the same amount of value merely change their form. In the one instance they exist in commodity-form, in the other in the form of money. What is really alienated by the seller, and, therefore, passes into the individual or productive consumption of the buyer, is the use-value of the commodity the commodity as a use-value. What, now, is the use-value which the money-capitalist gives up for the period of the loan and relinquishes to the productive capitalist the borrower? It is the use-value which the money acquires by being capable of becoming capital, of performing the functions of capital, and creating a definite surplus-value, the average profit (whatever is above or below it appears here as a mere accident) during its process, besides preserving its original magnitude of value. In the case of the other commodities the use-value is ultimately consumed. Their substance disappears, and with it their value. In contrast, the commodity-capital is peculiar in that its value and use-value not only remain intact but also increase, through consumption of its use-value. It is this use-value of money as capital this faculty of producing an average profit which the money-capitalist relinquishes to the industrial capitalist for the period, during which he places the loaned capital at the latter's disposal. Money thus loaned has in this respect a certain similarity with labour-power in its relation to the industrial capitalist. With the difference that the latter pays for the value of labour-power, whereas he simply pays back the value of the loaned capital. The use-value of labour-power for the industrial capitalist is that labour-power creates more value (profit) in its consumption than it possesses itself, and than it costs. This additional value is use-value for the industrial capitalist. And in like manner the use-value of loaned capital appears as its faculty of begetting and increasing value. The money-capitalist, in fact, alienates a use-value, and thus whatever he gives away is given as a commodity. It is to this extent that the analogy with a commodity per se is complete. In the first place, it is a value which passes from one hand to another. In the case of an ordinary commodity, a commodity as such, the same value remains in the hands of the buyer and seller, only in different forms; both have the same value which they had before the transaction, and which they had alienated the one in the form of a commodity, the other in the form of money. The difference is that in a loan the money-capitalist is the only one in the transaction who gives away value; but he preserves it through the prospective return. In the loan transaction just one party receives value, since only one party relinquishes value. In the second place, a real use-value is relinquished on the one side, and received and consumed on the other. But in contrast to ordinary commodities this use-value is value in itself, namely the excess over the original value realised through the use of money as capital. The profit is this use-value. The use-value of the loaned money lies in its being able to serve as capital and, as such, to produce the average profit under average conditions. What, now, does the industrial capitalist pay, and what is, therefore, the price of the loaned capital? 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 + M. Both of them, lender and borrower, expend the same sum of money as capital. But it is only in the hands of the latter that it serves as capital. The profit is not doubled by the double existence of the same sum of money as capital for two persons. It can serve as capital for both of them only by dividing the profit. The portion which falls to the lender is called interest. The entire transaction, as assumed, takes place between two kinds of capitalists the money-capitalist and the industrial or merchant capitalist. It must always be borne in mind that here capital as capital is a commodity, or that the commodity here discussed is capital. All the relations in evidence here would therefore be irrational from the standpoint of an ordinary commodity, or from that of capital in so far as it acts as a commodity-capital in the process of reproduction. Lending and borrowing, instead of selling and buying, is a distinction which here springs from the specific nature of the commodity-capital. Similarly, the fact that it is interest, not the price of the commodity, which is paid here. If we want to call interest the price of money-capital, then it is an irrational form of price quite at variance with the conception of the price of commodities. The price is here reduced to its purely abstract and meaningless form, signifying that it is a certain sum of money paid for something serving in one way or another as a use-value; whereas the conception of price really signifies the value of some use-value expressed in money. Interest, signifying the price of capital, is from the outset quite an irrational expression. The commodity in question has a double value, first a value, and then a price different from this value, while price represents the expression of value in money. Money-capital is nothing but a sum of money, or the value of a certain quantity of commodities fixed in a sum of money. If a commodity is loaned out as capital, it is only a disguised form of a sum of money. Because what is loaned out as capital is not so and so many pounds of cotton, but so much and so much money existing in the form of cotton as its value. The price of capital, therefore, refers to it as to a sum of money, even if not currency, as Mr. Torrens thinks (see Footnote 59). How, then, can a sum of value have a price besides its own price, besides the price expressed in its own money-form? Price, after all, is the value of a commodity (this is also true of the market-price, whose difference from value is not one of quality, but only one of quantity, referring only to the magnitude of value) as distinct from its use-value. A price which differs from value in quality is an absurd contradiction. Capital manifests itself as capital through self-expansion. The degree of its self-expansion expresses the quantitative degree in which it realises itself as capital. The surplus-value or profit produced by it its rate or magnitude is measurable only by comparison with the value of the advanced capital. The greater or lesser self-expansion of interest-bearing capital is, therefore, likewise only measurable by comparing the amount of interest, its share in the total profits, with the value of the advanced capital. If, therefore, price expresses the value of the commodity, then interest expresses the self-expansion of money-capital and thus appears as the price paid for it to the lender. This shows how absurd it is from the very first to apply hereto the simple relations of exchange through the medium of money in buying and selling, as Proudhon does. The basic premise is precisely that money functions as capital and may thus be transferred as such, i.e., as potential capital, to a third person. Capital, however, appears here as a commodity, inasmuch as it is offered on the market, and the use-value of money is actually alienated as capital. Its use-value, however, lies in producing profit. The value of money or of commodities employed as capital does not depend on their value as money or as commodities, but on the quantity of surplus-value they produce for their owner. The product of capital is profit. On the basis of capitalist production it is merely a different use of money whether it is expended as money; or advanced as capital. Money, or commodities, are in themselves potentially capital, just as labour-power is potential capital. Because, 1) money may be converted into elements of production and is, as is, merely an abstract expression of them their existence as value; 2) the material elements of wealth have the property of potentially becoming capital, because their supplementary opposite, which makes them into capital, namely wage-labour, is available on the basis of capitalist production. The contradictory social features of material wealth its antagonism to labour as wage-labour are expressed in capitalist property as such independently of the production process. This particular fact, set apart from the process of capitalist production itself, from which it constantly results and as whose constant result it serves as a constant prerequisite, expresses itself in that money and commodities alike are latent, potential, capital, so that they may be sold as capital, and in that they can in this form command the labour of others bestowing a claim to appropriate the labour of others, and therefore represent self-expanding values. It also becomes clearly apparent that this relationship, and not the labour offered as an equivalent on the part of the capitalist, supplies the title and the means to appropriate the labour of others. Furthermore, capital appears as a commodity, inasmuch as the division of profit into interest and profit proper is regulated by supply and demand, that is, by competition, just as the market-prices of commodities. But the difference here is just as apparent as the analogy. If supply and demand coincide, the market-price of commodities corresponds to their price of production, i.e., their price then appears to be regulated by the immanent laws of capitalist production, independently of competition, since the fluctuations of supply and demand explain nothing but deviations of market-prices from prices of production. These deviations mutually balance one another, so that in the course of certain longer periods the average market-prices equal the prices of production. As soon as supply and demand coincide, these forces cease to operate, i.e., compensate one another, and the general law determining prices then also comes to apply to individual cases. The market-price then corresponds even in its immediate form, and not only as the average of market-price movements, to the price of production, which is regulated by the immanent laws of the mode of production itself. The same applies to wages. If supply and demand coincide, they neutralise each other's effect, and wages equal the value of labour-power. But it is different with the interest on money-capital. Competition does not, in this case, determine the deviations from the rule. There is rather no law of division except that enforced by competition, because, as we shall later see, no such thing as a "natural" rate of interest exists. By the natural rate of interest people merely mean the rate fixed by free competition. There are no "natural" limits for the rate of interest. Whenever competition does not merely determine the deviations and fluctuations, whenever, therefore, the neutralisation of opposing forces puts a stop to any and all determination, the thing to be determined becomes something arbitrary and lawless. More on this in the next chapter. In the case of interest-bearing capital everything appears superficial: the advance of capital as mere transfer from lender to borrower; the reflux of realised capital as mere transfer back, as a return payment with interest, by borrower to lender. The same is true of the fact, immanent in the capitalist mode of production, that the rate of profit is not only determined by the relation of profit made in one single turnover to advanced capital-value, but also by the length of this period of turnover, hence determined as profit yielded by industrial capital within definite spans of time. In the case of interest-bearing capital this likewise appears on the surface to mean that a definite interest is paid to the lender for a definite time span. With his usual insight into the internal connection of things, the romantic Adam M ller says (Elemente der Staatskunst, Berlin, 1809, Dritter Theil, S. 138); He does not see how the time of production and the time of circulation enter into the determination of commodity-prices, and how this is just what determines the rate of profit for a given period of turnover of capital, whereas interest is determined by precisely this determination of profit for a given period. His sagacity here, as elsewhere, consists in observing the clouds of dust on the surface and presumptuously declaring this dust to be something mysterious and important. 
Economic Manuscripts: Capital, Vol.3, Chapter 21