The topic of population is treated only lightly in the major modern biographies of John Maynard Keynes, yet Keynes himself had strong - if varying - views on the subject. For many years he maintained a neo-Malthusian view of population, based on a postulated link between population growth and deteriorating terms of trade. This led him to take up a militant stance towards 'overpopulated' countries, notably India, China, and Egypt. Keynes on Population publishes two of John Maynard Keynes's manuscripts not published in the Collected Writings: his Cambridge lectures on population and 1914 Oxford lecture on 'Population'. It provides a detailed commentary on the text of 'Population' and discusses the extent of Keynes's engagement with the Social Darwinist doctrine of the 'rapid multiplication of the unfit' and with eugenics. It then traces the subsequent vicissitudes of his views on population and his interventions in the contemporary politics of population. These include his part in the 1920s campaign for birth control, the reversal of his neo-Malthusianism, and his eventual support for family allowances.