growing population except at an increased cost.[541] Now, if the supply is absolutely required, the most costly portion of it, whether it be got by an extension of cultivation to poorer lands, or by a more thorough cultivation of the richer, will determine the price of all the rest, for there cannot be two prices in the same market; and the profits of the producer of it will determine the profits of all his fellow-cultivators, for there cannot be two rates of profit in the same business. Furthermore, the agricultural profits will determine the rate in other businesses, for in a full-formed society the rate in the others must bear a fixed relation to the rate in this business, so that the one cannot materially vary without the other.[542] Therefore the greater cost of the last portion of the necessary supply of food will lower profits generally, will thereby increase the range of extra profits from the richer soils, and will thereby raise rents. The difference between the two men is, that what Malthus makes only one cause, Ricardo makes the only one, the increased cost of cultivation.[543] Ricardo and his friends have certainly put cause for effect.[544] It is of course in the first instance the high prices that lead to the costly cultivation, and not _vice versâ_, for without the high prices the produce of the costly cultivation would not be profitable. Malthus was asked by the Committee on Emigration: “Among other effects of resorting to a soil inferior to any now in cultivation, which is involved in the proposition of cultivating waste lands, would not one be to raise the rents of all the landlords throughout Great Britain and Ireland?”—He answered: “I think not. The cultivating of poor lands is not the cause of the rise of rents; the rise of the price of produce compared with the costs of production, which is the cause of the rise of rents, takes place first, and then such rise induces the cultivation of the poorer land. That is the doctrine I originally stated, and I believe it to be true; it was altered by others afterwards.”[545] On the other hand, what makes the high prices permanent instead of temporary, is the fact that the cultivation essential to the completeness of the supply cannot be other than costly.[546] It is, therefore, not wrong to consider costly cultivation as one cause of the permanence of high prices, and therewith of high rents. But Ricardo goes further, and counts it the only cause.