W. Otter, “Memoir,” preface to the 2nd ed. of the Principles of Political Economy (1836), is still a basis for any biography. James Bonar, Malthus and His Work (1885, reprinted and expanded 1924, reprinted 1966), is the major work of 19th-century scholarship, illuminated by very wide learning. John Maynard Keynes, “Robert Malthus: The First of the Cambridge Economists,” in Essays in Biography (new ed., 1951, reissued 1963), is charming and of great importance in the rehabilitation of Malthus as a major economic theorist. D.V. Glass (ed.), Introduction to Malthus (1953, reissued 1959), contains “A Summary View of the Principle of Population,” an important letter on the Poor Laws by Malthus, a very full bibliography on the Malthusian question in the 19th century, and three useful essays discussing Malthus in historical perspective. Anthony Flew, “The Structure of Malthus’ Population Theory,” Australasian Journal of Philosophy, 35:1–20 (1957), and the same author’s edited version of Malthus’s An Essay on the Principle of Population (1970, reissued 1985), were contributed by a critic and philosopher who has brought both logical rigour and sympathy to the clarification of Malthus’s analysis. Philip Morris Hauser and Otis Dudley Duncan (eds.), The Study of Population: An Inventory and Appraisal (1959, reissued 1964), though partly out of date, is a most useful single introduction to modern population studies and the issues raised by Malthus. Kenneth Smith, The Malthusian Controversy (1951, reprinted 1978); and D.E.C. Eversley, Social Theories of Fertility and the Malthusian Debate (1959, reprinted 1975), are two admirable and scholarly discussions of all the issues surrounding the Malthusian population theory. Also useful is Julian L. Simon, The Ultimate Resource 2 (1996, reissued 1998).