Adam Kucharski in Nautilus:
To say that Thomas Robert Malthus was unpopular would be putting it mildly. His 19th-century contemporary Percy Shelley, the revered poet, called him a eunuch and a tyrant. The philosopher William Godwin dubbed him “a dark and terrible genius that is ever at hand to blast all the hopes of all mankind.” As Malthus’ biographer later put it, he was the most abused man of his age. And that was the age of Napoleon Bonaparte. The catalyst for this vilification was the 1798 book An Essay on the Principle of Population. In it, Malthus—a curly haired, 32-year-old curate of a small English chapel—attacked the claims of utopian thinkers like Godwin, who believed that reason and scientific progress would ultimately create a perfect society, free of inequality and suffering. Malthus took a more pessimistic view. Using United States census data compiled by Benjamin Franklin, he predicted that the “passion of the sexes” would soon cause human populations to outstrip their resources, leading to poverty and hardship. If unchecked, people would continue to multiply exponentially, doubling every 25 years. Agricultural yields, however, would at best increase linearly, by a similar amount each year. In 100 years, Great Britain would have 16 times as many mouths to feed (112 million), but less than half enough food.
That didn’t happen, of course. By 1900, the British population had swelled only fivefold, to 35 million citizens, most of them well fed. But Malthus foresaw the possibility of this slowdown in growth, too. To prevent populations from booming and busting—the infamous “Malthusian catastrophe”—he said that Nature imposed two types of checks. “Preventive” checks reduced the birth rate: When times were hard, and food scarce, men—particularly poor men—would foresee the troubles ahead and delay getting married and starting families. “Positive” checks—famine, disease, murder, war—increased the death rate. Once food production caught up with demand, however, strife would lessen and families would grow. Thus the “grinding law of necessity, misery, and the fear of misery” kept the size of a population oscillating in sync with supply. To his critics’ disgust, Malthus used this theory to argue against England’s Poor Laws, which provided welfare to needy families according to the number of children they had. Why encourage the poor to procreate, he argued, when Nature will turn around and trample them?