Thomas Malthus (1766–1834) was an English clergyman whose theory on population, contained in An Essay on the Principle of Population (1798, and later revisions), has had a considerable impact on thinking about the limits of population growth. Malthus believed that unchecked population grows geometrically, a rate that surpasses the ability of the means of subsistence (e.g., food) to support it. To avoid overpopulation, two types of checks on population exist: preventive checks and positive checks. Preventive checks result from human actions that lower the birthrate; for Malthus, this largely meant the postponement of marriage to late ages. Positive checks include anything that operates to increase the death rate (e.g., war, famine, epidemics). While the operation of any of these checks reduces the rate of population growth, Malthus did not think that the preventive checks were powerful enough to prevent the population from growing faster than the means of subsistence. Sooner or later, the more drastic positive checks would come into play. Thus, humans were bound to over-reproduce and, in the end, human numbers would be reduced by increased deaths.
In the two centuries since the Essay was first published, the world's population has increased from less than 1 billion to more than 6 billion. While Malthusian theory is not a dominant theory of population growth in contemporary times, there is a group of neo-Malthusians who are concerned about this rate of population growth. They contend either that family planning and birth control are necessary to decrease fertility in third world countries or that war and other social ills are the result of scarcity and overpopulation. Contemporary neo-Malthusians include Lester Brown, Paul Ehrlich, and T. Fraser Homer-Dixon. Some leading opponents are Alexander Cockburn and Paul Athanasiou.
Brown, Lester, Gary Gardner, and Brian Halweil, eds. Beyond Malthus: Nineteen Dimensions of the Population Challenge. New York: Norton, 1999.
Malthus, Thomas R. Essay on the Principle of Population. Homewood, IL: R.D. Irwin, 1963.
ELLEN M. GEE