An erroneous conception of the nature of rent is based upon the fact that rent in kind, partly as tithes to the church and partly as a curiosity perpetuated by long-established contracts, has been dragged over into modern times from the natural economy of the Middle Ages, completely in contradiction to the conditions of the capitalist mode of production. It thereby creates the impression that rent does not arise from the price of the agricultural product, but from its mass, thus not from social conditions, but from the earth. We have previously shown that although surplus-value is manifested in a surplus-product the converse does not hold that a surplus-product, representing a mere increase in the mass of product, constitutes surplus-value. It may represent a minus quantity in value. Otherwise the cotton industry of 1860, compared with that of 1840, would show an enormous surplus-value, whereas on the contrary the price of the yarn has fallen. Rent may increase enormously as a result of a succession of crop failures, because the price of grain rises, although this surplus-value appears as an absolutely decreasing mass of dearer wheat. Conversely, the rent may fall in consequence of a succession of bountiful years, because the price falls, although the reduced rent appears as a greater mass of cheaper wheat. As regards rent in kind, it should be noted now that, in the first place, it is a mere tradition carried over from an obsolete mode of production and managing to prolong its existence as a survival. Its contradiction to the capitalist mode of production is shown by its disappearance of itself from private contracts, and its being forcibly shaken off as an anachronism, wherever legislation was able to intervene as in the case of church tithes in England. Secondly, however, where rent in kind persisted on the basis of capitalist production, it was no more, and could be no more, than an expression of money-rent in medieval garb. Wheat, for instance, is quoted at 40 shillings per quarter. One portion of this wheat must replace the wages contained therein, and must be sold to become available for renewed expenditure. Another portion must be sold to pay its proportionate share of taxes. Seed and even a portion of fertiliser enter as commodities into the process of reproduction, wherever the capitalist mode of production and with it division of social labour are developed, i.e., they must be purchased for replacement purposes; and therefore another portion of this quarter must be sold to obtain money for this. In so far as they need not be bought as actual commodities, but are taken out of the product itself in kind, in order to enter into its reproduction anew as conditions of production — as occurs not only in agriculture, but in many other lines of production producing constant capital — they figure in the books as money of account and are deducted as elements of the cost-price. The wear and tear of machinery, and of fixed capital in general, must be made good in money. And finally comes profit, which is calculated on this sum, expressed as costs either in actual money or in money of account. This profit is represented by a definite portion of the gross product, which is determined by its price. And the excess portion which then remains forms rent. If the rent in kind stipulated by contract is greater than this remainder determined by the price, then it does not constitute rent, but a deduction from profit. Owing to this possibility alone, rent in kind is an obsolete form, in so far as it does not reflect the price of the product, but may be greater or smaller than the real rent, and thus may comprise not only a deduction from profit, but also from those elements required for capital replacement. In fact, this rent in kind, so far as it is rent not merely in name but also in essence, is exclusively determined by the excess of the price of the product over its price of production. Only it presupposes that this variable is a constant magnitude. But it is such a comforting reflection that the product in kind should suffice, first, to maintain the labourer, secondly, to leave the capitalist tenant farmer more food than he needs, and finally, that the remainder should constitute the natural rent. Quite like a manufacturer producing 200,000 yards of cotton goods. These yards of goods not only suffice to clothe his labourers; to clothe his wife, all his offspring and himself abundantly; but also leave over enough cotton for sale, in addition to paying an enormous rent in terms of cotton goods. It is all so simple! Deduct the price of production from 200,000 yards of cotton goods, and a surplus of cotton goods must remain for rent. But it is indeed a naive conception to deduct the price of production of, say, £10,000 from 200,000 yards of cotton goods, without knowing the selling price, to deduct money from cotton goods, to deduct an exchange-value from a use-value as such, and thus to determine the surplus of yards of cotton goods over pounds sterling. It is worse than squaring the circle, which is at least based upon the conception that there is a limit at which straight lines and curves imperceptibly flow together. But such is the prescription of M. Passy. Deduct money from cotton goods, before the cotton goods have been converted into money, either in one’s mind or in reality! What remains is the rent, which, however, is to be grasped naturaliter (see, for instance, Karl Arnd [K. Arnd, Die naturgemässe Volkswirtschaft, gegenüber dem Monopoliengeiste und dem Communismus, Hanau, 1845, S. 461-62. — Ed.]) and not by deviltries of sophistry. The entire restoration of rent in kind is finally reduced to this foolishness, the deduction of the price of production from so many and so many bushels of wheat, and the subtraction of a sum of money from a cubic measure.