We have seen that interest-bearing capital, although a category which differs absolutely from a commodity, becomes a commodity sui generis, so that interest becomes its price, fixed at all times by supply and demand like the market-price of an ordinary commodity. The market rate of interest, while fluctuating continually, appears therefore at any given moment just as constantly fixed and uniform as the market-price of a commodity prevailing in each individual case. Money-capitalists supply this commodity, and functioning capitalists buy it, creating the demand for it. This does not occur when equalisation creates a general rate of profit. If prices of commodities in one sphere are below or above the price of production (wherein we deliberately leave aside the fluctuations attendant upon the various phases of the industrial cycle in each and every enterprise) the balance is effected through the expansion or curtailment of production, i.e., the expansion or curtailment of the masses of commodities thrown on the market by industrial capitals — caused by inflow or outflow of capital to and from individual spheres of production. It is by this equalisation of the average market-prices of commodities to prices of production that deviations of specific rates of profit from the general, or average, rate of profit are corrected. It cannot be that in this process industrial or mercantile capital as such should ever assume the appearance of commodities vis-à-vis the buyer, as in the case of interest-bearing capital. If perceptible at all, this process is so only in the fluctuations and equalisations of market-prices of commodities to prices of production, not as a direct fixation of the average profit. The general rate of profit is, indeed, determined 1) by the surplus-value produced by the total capital, 2) by the proportion of this surplus-value to the value of the total capital, and 3) by competition, but only in so far as this is a movement whereby capitals invested in particular production spheres seek to draw equal dividends out of this surplus-value in proportion to their relative magnitudes. The general rate of profit, therefore, derives actually from causes far different and far more complicated than the market rate of interest, which is directly and immediately determined by the proportion between supply and demand, and hence is not as tangible and obvious a fact as the rate of interest. The individual rates of profit in various spheres of production are themselves more or less uncertain; but in so far as they appear, it is not their uniformity but their differences which are perceptible. The general rate of profit, however, appears only as the lowest limit of profit, not as an empirical, directly visible form of the actual rate of profit.