Calls for increased public participation in science and technology policy are now commonplace and raise challenges for social scientists as well as policy-makers. For social scientists, the practice of public participation raises questions about the methods used by social scientists to collect data and develop the representations of public opinion that inform this new dialogue but also reflect it. In this paper, the difference that different methods can make is illustrated by comparing the focus group data on perceptions of stem cell research with the more conventional survey based representations of public opinion. By examining how our data allow the uncertainty and ambivalence of participants to remain visible in its analysis, we argue that a more qualitatively informed social science can contribute to public debate in ways that go beyond the quantification of ‘pro’ and ‘anti’ positions that survey research appears to encourage. In particular, we argue that by providing, and in some sense sustaining, alternative representations of public concerns that resist polarization, social science can inform a more broad-ranging ‘upstream’ debate about the social purposes that science should serve. … there is nothing a government hates more than to be well-informed; for it makes the process of arriving at decisions much more complicated and difficult (John Maynard Keynes, quoted in Skidelsky, 1992, p. 630).