An Essay on the Principle of Population
The work was cited by Adam Smith in his "Wealth of Nations", in Ezra Stiles's "Discourse on the Christian Union", and in Richard Price's "Observations on Reversionary Payments". It also influenced David Hume, Samuel Johnson, and William Godwin. The notion of the population doubling every 25 years influenced Thomas Malthus, who quotes paragraph 22 of the essay, with attribution, in his 1802 work "An Essay on the Principle of Population". Through Malthus, the essay is said to have influenced Charles Darwin. Conway Zirkle has noted that "Franklin is really the source of Darwin's inspiration, for he gave Malthus the clue to the theory of population we now call Malthusian, and Malthus... gave Darwin the clue which led to the discovery of natural selection."