The argument of Malthus concerned the lack of food and housing for the-then rapidly rising population of the United Kingdom. Malthus predicted that overpopulation would result in large scale civil strife, malnutrition and starvation; the level of population having outstripped the productive capacity of all arable land.
Although much of the credit for theory behind rental levels went to Malthus's contemporary Ricardo, this essay remains an important contribution to economic literature. Malthus was in concurrence with the Physiocrats, who posited that land produced more than enough to maintain those tilling it. Malthus however observed that population rose faster than the actual supply of food - thus, demand for agricultural goods rose consistently.
Malthus also discusses the differing nature of land - some is farmed better and more ably, is more fertile, and holds greater resistance to poor seasons or unusual weather. The difference between the raw productivity of the farmer's land and the capital generated was thus his rent - for greater or smaller.
Also known by its full title, An Inquiry into the Nature and Progress of Rent, this essay had a great influence upon the economists in and beyond the 19th century.