The proof that the earth’s fertility, taken by itself, can never be the cause of rent is easily seen in the case of a new country. In a newly founded colony, for example, land yields no rent, however fertile, if the quantity of land is in excess of the people’s demand. “For no one would pay for the use of land when there was an abundant quantity not yet appropriated, and therefore at the disposal of whosoever might choose to cultivate it.”[319] Rent only appears “when the progress of population calls into cultivation land of an inferior quality or less advantageously situated.” Here we have the very kernel of Ricardo’s theory. Instead of being an indication of nature’s generosity, rent is the result of the grievous necessity of having recourse to relatively poor land under the pressure of population and want.[320] “Rent is a creation of value, not of wealth,” says Ricardo—a profound saying, and one that has illuminated many a mystery attaching to the theory of rent. In that sentence he draws a distinction between wealth born of abundance and satisfaction and value begotten of difficulty and effort, and he declares that rent is of the second category and not of the first. Still, this cannot be accepted as the final explanation. It is difficult to understand how a purely negative condition such as the absence of fertile land could ever create a revenue. It were better to say that the want of suitable land supplies the occasion for the appearance of rent, although it is not its cause. The cause is the high price of agricultural products—say corn—due to the increased difficulty of cultivating the less fertile lands.[321] In short, the cause and the measure of the rent of corn-land are determined by the quantity of labour necessary to produce corn under the most unfavourable circumstances, “meaning by the most unfavourable circumstances the most unfavourable under which the quantity of produce required renders it necessary to carry on production.”[322]