'An Essay on the Principle of Population': population outruns subsistence
The argument that population, if nothing checks it, grows faster than the means of subsistence: population in a geometrical ratio, subsistence in an arithmetical one. It follows that want, disease, war and famine inevitably cut the increase back.
The argument was put forward in 1798 by the English cleric and economist Thomas Robert Malthus in answer to Godwin and Condorcet. The book was political economy and an argument about poverty, not natural history.
But its reasoning about 'positive checks' and the unavoidable overproduction of offspring was read by two naturalists, Darwin in 1838 and Wallace in 1858, and each carried it over to animals and plants: if more are born than can survive, survival is not random. Thus a book about poor parishes became the quantitative premise of the struggle for existence.
Why this date
The date follows the first, anonymous edition of 1798 ('An Essay on the Principle of Population, as It Affects the Future Improvement of Society, with Remarks on the Speculations of Mr. Godwin, M. Condorcet, and Other Writers', London, J. Johnson). What Darwin read in 1838 was not the first but the sixth edition (1826), as Sloan notes in the Stanford Encyclopedia; the axis takes the year of first publication.
What grew out of it
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'On the Origin of Species': natural selection as the mechanism of species formation
influenced · Confidence: high
Darwin already knew from the breeders that selection accumulates characters, but did not see how selection could act in nature; reading Malthus in the autumn of 1838 gave him the missing link, the overproduction of offspring and the struggle for existence, and he himself repeatedly called this the moment when he 'had at last got a theory by which to work'.
Dispute: Neither the reading of Malthus nor its turning-point character is contested; the argument is over what exactly Darwin took from him and how decisive that was. One line of historiography (Young, 'Darwin's Metaphor', 1985; Desmond and Moore) derives the theory from British political economy and stresses that Malthusian ideas were commonplace in Darwin's circle long before 1838: Desmond in Britannica calls it 'a seminal moment' but adds at once that Malthusianism 'had long permeated his Whig circle'. Another line (Bowler, 'Malthus, Darwin, and the concept of struggle', Journal of the History of Ideas 37, 1976; Schweber, Journal of the History of Biology 13, 1980) insists that Malthus's 'struggle' and Darwin's are not the same thing, and that by September 1838 Darwin already had most of the components of the theory, so that Malthus supplied a trigger rather than content. Sloan in the Stanford Encyclopedia notes that recent manuscript-based work has 'de-emphasized some of the novelty of Darwin's views'. The date is also inconsistent: Darwin in the Autobiography writes 'October 1838', Desmond in Britannica gives September 1838, Sloan August 1838; by Notebook D the reading is placed on 28 September 1838.
Link sources
- Phillip Sloan, Darwin: From the Origin of Species to the Descent of Man, Stanford Encyclopedia of Philosophy (2019) Verified 20 Sep 2026
This concern with a causal theory of life was then replaced by a new emphasis on external forces controlling population, a thesis developed from his reading of Thomas Malthus's (1766–1834) Essay on the Principle of Population (6th ed. 1826).
- Phillip Sloan, Darwin: From the Origin of Species to the Descent of Man, Stanford Encyclopedia of Philosophy (2019) Verified 20 Sep 2026
The impact of Darwin's reading of this edition of the Essay in August of 1838, was dramatic. It enabled him to theorize the existence of a constantly-acting dynamic force behind the transformation of species. Darwin's innovation was to universalize the Malthusian "principle of population" to apply to all of nature.
- Charles Darwin, Evolution by natural selection: the London years, 1836-42, Encyclopaedia Britannica (Adrian J. Desmond) (2026) Verified 24 Sep 2026
But he only saw the complete congruity between the way nature operated and the way fanciers produced new breeds upon reading the economist Thomas Malthus's Essay on the Principle of Population in September 1838.
- Charles Darwin, Evolution by natural selection: the London years, 1836-42, Encyclopaedia Britannica (Adrian J. Desmond) (2026) Verified 24 Sep 2026
Darwin realized that population explosions would lead to a struggle for resources and that the ensuing competition would weed out the unfit. It was an idea he now applied to nature (he had previously thought that animal populations remained stable in the wild). Darwin called his modified Malthusian mechanism "natural selection."
- Nora Barlow (ed.), The Autobiography of Charles Darwin 1809-1882, London: Collins, p. 120 (Darwin Online, F1497) (1958) Verified 20 Sep 2026
In October 1838, that is, fifteen months after I had begun my systematic enquiry, I happened to read for amusement Malthus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The result of this would be the formation of new species. Here, then, I had at last got a theory by which to work
- Charles Darwin to A. R. Wallace, 6 April 1859, Darwin Correspondence Project, DCP-LETT-2449 (1859) Verified 20 Sep 2026
You are right, that I came to conclusion that Selection was the principle of change from study of domesticated productions; & then reading Malthus I saw at once how to apply this principle.
- Charles Darwin, On the Origin of Species, 1st ed., Introduction, p. 5 (Darwin Online, F373) (1859) Verified 20 Sep 2026
This is the doctrine of Malthus, applied to the whole animal and vegetable kingdoms.
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.
- Phillip Sloan, Darwin: From the Origin of Species to the Descent of Man, Stanford Encyclopedia of Philosophy (2019) Verified 20 Sep 2026
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Wallace, 'On the Tendency of Varieties to Depart Indefinitely from the Original Type': natural selection found independently
influenced · Confidence: high
By Wallace's own account, the idea of the survival of the fittest came to him in a fever in the Moluccas when he recalled Malthus's 'positive checks' on population and realised that the same causes act still more strongly on animals; historians accept the account, and Malthus is among the books that 'profoundly influenced' Wallace as early as the 1840s.
Dispute: The only evidence for Malthus's part in the insight of 1858 is Wallace's own accounts, the fullest of them written in 1905, 47 years later; the manuscript and covering letter are lost. Smith (2014) warns that Wallace in his recollections tends to compress separate events into a single sentence, and that van Wyhe questions the accuracy of his memory on this ground, though Smith himself puts it down to writing style rather than faulty memory. The origin of the idea itself is also argued: Costa (2013) holds that the Ternate paper was written as a response to Lyell's anti-evolutionary chapters rather than derived from Malthus; the paper does not name Malthus, although its reasoning about geometrical increase and that 'twice that number must perish annually' is plainly Malthusian.
Link sources
- A. R. Wallace, My Life: A Record of Events and Opinions, London: Chapman & Hall, vol. 1, pp. 361-363 (1905) Verified 20 Sep 2026
One day something brought to my recollection Malthus's "Principles of Population," which I had read about twelve years before. I thought of his clear exposition of "the positive checks to increase"-disease, accidents, war, and famine-which keep down the population of savage races to so much lower an average than that of civilized peoples. It then occurred to me that these causes or their equivalents are continually acting in the case of animals also; and as animals usually breed much more rapidly than does mankind, the destruction every year from these causes must be enormous in order to keep down the numbers of each species
- A. R. Wallace, My Life: A Record of Events and Opinions, London: Chapman & Hall, vol. 1, pp. 361-363 (1905) Verified 20 Sep 2026
Then it suddenly flashed upon me that this self-acting process would necessarilyimprove the race, because in every generation the inferior would inevitably be killed off and the superior would remain-that is, the fittest would survive.
- Alfred Russel Wallace's essay on varieties, Darwin Correspondence Project (2024) Verified 20 Sep 2026
Wallace's essay was written in February 1858. He recollected the events surrounding its composition in his autobiography (Wallace 1905, 1: 361-3)
- H. Lewis McKinney, Wallace, Alfred Russel, Complete Dictionary of Scientific Biography (1976) Verified 20 Sep 2026
indeed, during the period from 1842 to 1846, he consumed various works by Alexander von Humboldt, T. R. Malthus, Charles Darwin, Robert Chambers, Charles Lyell, and William Swainson. These books profoundly influenced his subsequent intellectual development
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.
- A. R. Wallace, My Life: A Record of Events and Opinions, London: Chapman & Hall, vol. 1, pp. 361-363 (1905) Verified 20 Sep 2026
Node sources
- Thomas Malthus, Encyclopaedia Britannica (2024) Verified 20 Sep 2026
In 1798 Malthus published anonymously the first edition of An Essay on the Principle of Population as It Affects the Future Improvement of Society, with Remarks on the Speculations of Mr. Godwin, M. Condorcet, and Other Writers.
- Thomas Malthus, Encyclopaedia Britannica (2024) Verified 20 Sep 2026
The increase of population will take place, if unchecked, in a geometric progression, while the means of subsistence will increase in only an arithmetic progression. Population will always expand to the limit of subsistence.
- Phillip Sloan, Darwin: From the Origin of Species to the Descent of Man, Stanford Encyclopedia of Philosophy (2019) Verified 5 Oct 2026
For Malthus, human populaton was assumed to expand geometrically, while food supply expanded arithmetically, leading to an inevitable struggle of humans for existence.
- T. R. Malthus, An Essay on the Principle of Population, 1st ed., London: J. Johnson (1798) Verified 5 Oct 2026
An Essay on the Principle of Population
"Verified" means that on that day the quotation was found at the address given, word for word. No date means we have not been able to open the source yet, not that the quotation is wrong.