What Malthus Missed

Though John Maynard Keynes had the highest opinion of his contributions to economics, Malthus continues to be bad-mouthed by many of today's sociologists and economists. The passion displayed by some of his detractors is grossly disproportionate to the magnitude of his errors. A conscientious listing of the explicit statements made by Malthus would, I am sure, show that far more than 95 percent of them are correct. But for any writer who becomes notorious for voicing unwelcome "home truths," a correctness score of 95 percent is not enough. Envy, an all-toohuman failing, is not unknown among critics. Envy sharpens the critical faculties but dulls the sense of proportion. The potentially unlimited growth of debt through the exponential growth of usury is counterbalanced, as we have seen, by such factors as bankruptcy, repudiation of debts, and inflation. Potentially exponential biological reproduction is also kept in check by counterbalancing forces. Every species "seeks" to convert the matter of its surroundings ("the environment") into more of its own kind, without limit. But since the amount and quality of convertible matter does have limits, so also must the growth of every population be limited. What in fact does limit the growth of populations? Malthus was concerned only with the human species. Having found a mathematical expression for reproduction he then sought another mathematical expression for the limitation to human fertility. No one thinks he was successful in this second endeavor. We note that as a student at Cambridge he was graduated as Ninth Wrangler. The quaint term "wrangler" is awarded by the English to someone who takes honors in mathematics. Since Malthus placed ninth in his class we may assume that he was only modestly endowed with mathematical ability. We should not be surprised to learn that he made a serious mistake in applying mathematics to the problem of the factors limiting human populations. (Look again at Box 9-1 on page 88.)