At its core, Malthusian theory asserts that population growth is inevitable whenever conditions are right. In other words, provided enough subsistence and stability, humanity will always tend toward multiplication. Since population grows at an exponentially faster rate than food production, a drop in the price of provisions will prompt a rise in birth rate, and this increase in the demand for food will soon negate any benefit from the initial price drop. Any additional population increase can be kept in check by active prevention (e.g., abstinence due to the incapacity of raising a family) or by forces such as natural disasters (e.g., epidemics arising from cramped and insalubrious living conditions). From these observations, Malthus concludes that the human condition, and society as a whole, always tends toward the level of subsistence.

Modern economists have deemed Malthus’s theory as deterministic. Although human action has some degree of power over change, the superior power of population will ensure that any societal progress toward abundance will inevitably be kept back by uncontrollable birth rates. Furthermore, Malthus comments that the greatest bouts of misery, which act as a check to population by increasing mortality rates, are mostly endured by the lower classes. This is dubbed the Malthusian catastrophe.