With world population today edging over seven billion, and with projections for it to reach nine billion by mid-century, the ideas of eighteenth-century English cleric Thomas Malthus-and his grim prediction that war, plague, and famine are the inevitable response to overpopulation--loom ever larger on the horizon. But if Malthus is a familiar name to most educated people, few of us have read his famous and controversial work, Essay on the Principle of Population, and indeed few have but a sketchy notion of his ideas. In this Very Short Introduction, Donald Winch explains and clarifies Malthus's thought, assessing the profound influence he has had on modern economics. Concentrating on his writings, Winch sheds light on the context in which he wrote and why his work has remained controversial. Looking at Malthus's early life as well as the evolution of his theories from population to political economy, Winch considers why and how Malthus's writings have been so influential in the thought of later figures such as Charles Darwin and John Maynard Keynes.