The emergence of the eugenic movement in the late nineteenth century reflected a concern with the perceived negative consequences of differential fertility for the quality of human populations. As theory, eugenics was based on little science and a good measure of racial and class prejudice. As an ameliorative program, even in its own terms, it was patently marginal, aiming as it did at discouraging reproduction among the unfit, as defined by medical criteria. By the 1930s, even to adherents of the faith, such “negative eugenics” seemed increasingly irrelevant as a response to the dominant Western demographic trend: a drastic fall of fertility, foreshadowing an absolute decline in population numbers. In the 1935 Gallon Lecture to the Eugenics Society, Alexander Carr-Saunders (1886–1966), probably the best-known British demographer of the interwar years, and also a prominent member of the Society, presented a vigorous critique of negative eugenics. The declining birth rate, he argued, no longer permits neglect of quantitative aspects of population, but calls for a positive eugenics: efforts “to raise the fertility of those who are not definitely subnormal until at least they replace themselves.” The specifics of the program he set forth, however, represent not a shift in emphasis but a clear break with eugenic concerns. He advocates a “scientific population policy,” the central thrust of which would be removing obstacles to and creating facilities for the fulfillment of the social duty of reproduction within a system of voluntary parenthood–measures widely espoused today in low-fertility societies. With the omission of the closing sections, the lecture is reproduced below from Eugenics Review, 1935, vol. 27, no. 1.