The book An Essay on the Principle of Population was first published in 1798 under the alias Joseph Johnson, but the author was soon identified as Thomas Robert Malthus. While it was not the first book on population, it has been acknowledged as the most influential work of its era. Its 6th edition was independently cited as a key influence by both Charles Darwin and Alfred Russel Wallace in developing the theory of natural selection.

A key portion of the book was dedicated to what is now known as Malthus' Iron Law of Population. This name itself is retrospective, based on the iron law of wages, which is the reformulation of Malthus' position by Ferdinand Lassalle, who in turn derived the name from Goethe's "great, eternal iron laws" in Das Göttliche. This theory suggested that growing population rates would contribute to a rising supply of labour that would inevitably lower wages. In essence, Malthus feared that continued population growth would lend itself to poverty.

One immediate impact of Malthus's book was that it fueled the debate about the size of the population in Britain and led to (or at least greatly accelerated) the passing of the Census Act 1800. This Act enabled the holding of a national census in England, Wales and Scotland, starting in 1801 and continuing every ten years to the present.

In 1803, Malthus published a major revision to his first edition, as the same title second edition; his final version, the 6th edition, was published in 1826. However, in 1830, 32 years after the first edition, Malthus published a condensed version titled A Summary View on the Principle of Population, which included remarks about criticisms of the main book.

The book An Essay on the Principle of Population was first published in 1798 under the alias Joseph Johnson, but the author was soon identified as Thomas Robert Malthus. While it was not the first book on population, it has been acknowledged as the most influential work of its era. Its 6th edition was independently cited as a key influence by both Charles Darwin and Alfred Russel Wallace in developing the theory of natural selection.

A key portion of the book was dedicated to what is now known as Malthus' Iron Law of Population. This name itself is retrospective, based on the iron law of wages, which is the reformulation of Malthus' position by Ferdinand Lassalle, who in turn derived the name from Goethe's "great, eternal iron laws" in Das Göttliche. This theory suggested that growing population rates would contribute to a rising supply of labour that would inevitably lower wages. In essence, Malthus feared that continued population growth would lend itself to poverty.

One immediate impact of Malthus's book was that it fueled the debate about the size of the population in Britain and led to (or at least greatly accelerated) the passing of the Census Act 1800. This Act enabled the holding of a national census in England, Wales and Scotland, starting in 1801 and continuing every ten years to the present.

In 1803, Malthus published a major revision to his first edition, as the same title second edition; his final version, the 6th edition, was published in 1826. However, in 1830, 32 years after the first edition, Malthus published a condensed version titled A Summary View on the Principle of Population, which included remarks about criticisms of the main book.

Thomas Robert Malthus (13 February 1766–23 December 1834) was an English cleric and scholar, influential in the fields of political economy and demography. Malthus himself used only his middle name Robert.

His An Essay on the Principle of Population observed that sooner or later population will be checked by famine and disease, leading to what is known as a Malthusian catastrophe. He wrote in opposition to the popular view in 18th-century Europe that saw society as improving and in principle as perfectible. He thought that the dangers of population growth precluded progress towards a utopian society: "The power of population is indefinitely greater than the power in the earth to produce subsistence for man". As a cleric, Malthus saw this situation as divinely imposed to teach virtuous behaviour. Malthus wrote:

That the increase of population is necessarily limited by the means of subsistence,

That population does invariably increase when the means of subsistence increase, and,

That the superior power of population is repressed, and the actual population kept equal to the means of subsistence, by misery and vice.

Malthus placed the longer-term stability of the economy above short-term expediency. He criticized the Poor Laws, and (alone among important contemporary economists) supported the Corn Laws, which introduced a system of taxes on British imports of wheat. His views became influential, and controversial, across economic, political, social and scientific thought. Pioneers of evolutionary biology read him, notably Charles Darwin and Alfred Russel Wallace. He remains a much-debated writer.