人口論
Thomas Malthus, an Anglican clergyman, statistician, and economist, argued in "An Essay on the Principle of Population" (1798) that population growth generally expanded exponentially in times and in regions of plenty until the size of the population quickly outstripped resources of subsistence. According to him, there were two types of checks that served to hold population within resource limits: "positive" checks, which raise the death rate; and "preventive" ones, which lower the birth rate. The positive checks include hunger, disease and war; the preventive checks, abortion, birth control, prostitution, postponement of marriage and celibacy. As a clergyman Malthus condemned birth control as "morally indefensible along with infanticide, abortion, and adultery."