Malthus's demographic theory, presented in his Essay on the Principle of Population, argues that population growth tends to outstrip the growth of resources, especially food, leading to a struggle for survival. He suggested that population growth would be controlled by "positive checks" such as famine, disease, and war.

Key Elements of Malthus's Theory:

• Geometric vs. Arithmetic Growth: Malthus believed that population grows exponentially (geometrically), while resources, particularly food, grow linearly (arithmetically).

• Positive Checks: These are events like famine, disease, and war, which Malthus argued would occur when population exceeds resources.

• Preventive Checks: Malthus also mentioned "preventive checks," such as delayed marriage or abstinence, which limit birth rates, but he believed they were less effective than positive checks.

Criticisms of Malthus's Theory:

• Technological Advancements: Malthus did not account for technological advances, particularly in agriculture, which have increased food production.

• Social and Economic Factors: Critics argue that Malthus oversimplified the relationship between population, resources, and living standards, neglecting social inequality, economic development, and government policies.

Neo-Malthusian Perspective:
Later thinkers, called Neo-Malthusians, emphasized preventive checks, like contraception and family planning, rather than relying solely on positive checks.

In essence, Malthus's theory highlighted the risks of overpopulation, but it has been debated and revised due to technological progress and the complexities of human behavior and social systems.