His book commences with a single elementary proposition, that man desires to maintain and improve his condition, whether physical, moral, intellectual, or political: and the object of it is to show, that the theories of Mr. Malthus and Mr. Ricardo are in direct opposition to the universal fact, and therefore cannot be regarded as natural laws. On the contrary, he shows that food has always grown faster than population, and that the power to obtain subsistence has always increased most rapidly in those countries, and at those times, in which population has most rapidly increased, and in which cultivation has most rapidly extended over those soils denominated by Mr. Ricardo inferior. The error of all these writers is shown to be in taking _quantities_ instead of _proportions_, and it is the law of proportions that constitutes the novel feature of this work. Ricardo and Malthus assert that land, labor, and capital are the agents of production, and are subject to different laws, all tending to produce contrariety of interests, and that the reason why such is the case is that land owes its value--or power to command rent for its use--to _monopoly_, while capital is the accumulated product of labor. Mr. Carey, on the contrary, shows, by a vast variety of facts, that land owes its value to labor alone, and that its selling price is _invariably_ less than would purchase the quantity of labor required to induce its present condition were it restored to a state of nature. It is, therefore, like steam-engines, mills, or ships, to be considered as capital, the interest upon which is called rent, and it is subject to the same laws as capital in any other form. With the growth of wealth and population, the landlord is shown to be receiving a constantly decreasing _proportion_ of the product of labor applied to cultivation, but a constantly increasing _quantity_, because of the rapid increase in the amount of the return as cultivation is improved and extended.[27] So it is with the capitalist. The _rate_ of interest falls as cultivation is improved, and capital is accumulated with greater facility, and the capitalist receives a smaller _proportion_; but the _quantity_ of commodities obtainable in return for the use of a given amount of capital increases, and with every change in that direction there is shown to be an increasing tendency to equality and to improvement of condition, physical, moral, intellectual, and political.