Q.State Malthus' theory of population in one sentence.

Malthus made one of the most famous, and most pessimistic, arguments in classical economics.

In his 1798 An Essay on the Principle of Population, Thomas Robert Malthus argued that human population, left unchecked, has the tendency to increase geometrically (doubling every generation: 1, 2, 4, 8, 16 …), while the food supply, limited by the availability of land and subject to diminishing returns, can at best increase only arithmetically (1, 2, 3, 4, 5 …). Because population growth would then always tend to outpace the growth of food supply, Malthus argued that population is eventually brought back into balance with food supply either through 'positive checks' — famine, disease and war, which raise the death rate — or through 'preventive checks' — late marriage and moral restraint, which lower the birth rate. Malthus' specific numerical prediction did not come true for most of the world because of large, unforeseen gains in agricultural productivity, but his underlying warning about the tension between population growth and finite resources remains a reference point in discussions of sustainable development.