In whatever order the lands come into cultivation, those which when cultivated yield the least return, in proportion to the labor required for their culture, will always regulate the price of agricultural produce; and all other lands will pay a rent simply equivalent to the excess of their produce over this minimum. Whatever unguarded expressions may have been occasionally used in describing the law of rent, these two propositions are all that was ever intended by it. If, indeed, Mr. Carey could show that the return to labor from the land, agricultural skill and science being supposed the same, is not a diminishing return, he would overthrow a principle much more fundamental than any law of rent. But in this he has wholly failed. Another objection taken against the law of diminishing returns, and so against the law of rent, is that the potential increase of food, e.g., of a grain of wheat, is far greater than that of man.(183) No one disputes the fact that one grain of wheat can reproduce itself more times than man, and that too in a geometric increase; but not without land. A grain of wheat needs land in which it can multiply itself, and this necessary element of its increase is limited; and it is the very thing which limits the multiplication of the grains of wheat. On the same piece of land, one can not get more than what comes from one act of reproduction in the grain. If one grain produces 100 of its kind, doubling the capital will not repeatedly cause a geometric increase in the ratio of reproduction of each grain on this same land, so that one grain, by one process, produces of its kind 200, 400, 800, or 1,600, because you can not multiply the land in any such ratio as would accompany this potential reduplication of the grain. This objection would not seem worth answering, were it not that it furnishes some difficulty to really honest inquirers. Others, again, allege as an objection against Ricardo, that if all land were of equal fertility it might still yield a rent. But Ricardo says precisely the same. It is also distinctly a portion of Ricardo’s doctrine that, even apart from differences of situation, the land of a country supposed to be of uniform fertility would, all of it, on a certain supposition, pay rent, namely, if the demand of the community required that it should all be cultivated, and cultivated beyond the point at which a further application of capital begins to be attended with a smaller proportional return.