Final answer:
Thomas Malthus made dire predictions about the earth's ability to sustain its growing population based on his theory of positive and preventive checks. He believed that war, famine, and disease would increase mortality rates to control the population, while birth control and celibacy would reduce fertility rates. Malthus predicted that if the population continued to grow exponentially, people would eventually run out of food and start starving.
Step-by-step explanation:
Thomas Malthus (1766-1834) was an English clergyman who made dire predictions about earth's ability to sustain its growing population. According to Malthusian theory, three factors would control human population that exceeded the earth's carrying capacity, or how many people can live in a given area considering the amount of available resources. Malthus identified these factors as war, famine, and disease (Malthus 1798). He termed them "positive checks" because they increase mortality rates, thus keeping the population in check. They are countered by "preventive checks," which also control the population but by reducing fertility rates; preventive checks include birth control and celibacy. Thinking practically, Malthus saw that people could produce only so much food in a given year, yet the population was increasing at an exponential rate. Eventually, he thought people would run out of food and begin to starve. They would go to war over increasingly scarce resources and reduce the population to a manageable level, and then the cycle would begin anew.