Rent, Anderson argued, was a charge for the use of the more fertile soil. The least fertile soils in cultivation generated an income that simply covered the costs of production, while the more fertile soils received a "certain premium for an exclusive privilege to cultivate them; which will be greater or smaller according to the more or less fertility of the soil. It is this premium which constitutes what we now call rent; a medium by means of which the expence () of cultivating soils of very different degrees of fertility may be reduced to a perfect quality." Anderson argued that improvement of the soil was possible; but also that humans could degrade the soil. He argued also that since where farm land in England was held by capitalists, the farmer would tend to avoid improvements the full return for which would not be received during the lease.