The requisites of production being labor, capital, and natural agents, the only person, besides the laborer and the capitalist, whose consent is necessary to production, and who can claim a share of the produce as the price of that consent, is the person who, by the arrangements of society, possesses exclusive power over some natural agent. The land is the principal of the natural agents which are capable of being appropriated, and the consideration paid for its use is called rent. Landed proprietors are the only class, of any numbers or importance, who have a claim to a share in the distribution of the produce, through their ownership of something which neither they nor any one else have produced. If there be any other cases of a similar nature, they will be easily understood, when the nature and laws of rent are comprehended. It is at once evident that rent is the effect of a monopoly. The reason why land-owners are able to require rent for their land is, that it is a commodity which many want, and which no one can obtain but from them. If all the land of the country belonged to one person, he could fix the rent at his pleasure. This case, however, is nowhere known to exist; and the only remaining supposition is that of free competition; the land-owners being supposed to be, as in fact they are, too numerous to combine. The ratio of the land to the cultivators shows the limited quantity of land. It is very desirable to keep the connection of one part of the subject with another wherever possible. “Agricultural rent, as it actually exists,” says Mr. Cairnes,(180) truly, “is not a consequence of the _monopoly_ of the soil, but of its diminishing productiveness.” The doctrine of rent depends upon the law of diminishing returns; and it is only by the pressure of population upon land that the lessened productiveness of land, whether because of poorer qualities or poorer situations, is made apparent. Or, to take things in their natural sequence, an increase of population necessitates more food; and this implies a resort to more expensive methods, or poorer soils, so soon as land is pushed to the extent that it will not yield an increased crop for the same application of labor and capital as formerly. Different qualities of land, then, being in cultivation at the same time, the better qualities must, of course, yield a greater return than the poorer, and the conditions then exist under which land pays rent. Those, therefore, who admit the law of diminishing returns are inevitably led to the doctrine of rent. § 2. No Land can pay Rent except Land of such Quality or Situation as exists in less Quantity than the Demand.