Thomas Malthus' theory of population proposed that, while the human population grows exponentially, food production grows arithmetically. Hence, at some point humans might face having too few resources to survive. Malthus believed that controlling population growth would help to avoid this catastrophe.
Malthus published his theory in 1798. He felt that the best method of controlling the population would be for men to marry later in life, which would lead to smaller families and prevent excessive population growth. However, Malthus did not support married couples using birth control. He also identified what he called positive checks to population growth, including disease, famine and poor standards of living. These positive checks to growth were phenomena that actively reduced the population.
Malthus supported welfare reform, arguing that providing more welfare to larger families provided an incentive for couples to keep having children. He felt that if the government gave more welfare to the poor, prices would rise, and nobody would be better off. Malthus supported capitalism, although he was concerned that as population growth outpaced production, demand would increase, and prices would rise.
Malthus continued to update his theories until 1826. He died in England in 1834, having helped demographics become a serious academic discipline.