I examine and propose a solution to tensions between two approaches to understanding scientific inquiry: sociological description and normative epistemology. The two clash over the relation of epistemic standards distinguishing scientific knowledge from opinion to our pervasively social scientific practices. An adequate epistemology of scientific inquiry must explicate this relation. Yet the normative/descriptive gap with respect to the social aspects of science polarizes epistemology of scientific inquiry into two mutually exclusive, unsatisfactory projects: elaboration of abstract epistemic ideals with no clear relation to our scientific practices, or description of socio-historical facts of no clear epistemic significance. I argue that this dilemma is unresolved by existing accounts, including those of Bloor (1991), Fleck (1979[1935]), Goldman (1999), Kitcher (1993, 2001), Longino (1990, 2002), Shapin (1994) and Solomon (2001). I then propose a solution, grounded in the meta-epistemological commitments of experimental research. This positive account bridges the gap between our scientific practices and epistemic ideals by integrating the two within a consensus framework drawn from philosophy of social action. On this view, scientific practices are conceived as social actions aimed at shared goals, constrained by minimal preconditions for instrumental rationality. I then apply this framework to a recent episode of immunology: the search for blood stem cells. Linked to mid-20th century cell biology, genetics and radiation research, this line of immunological inquiry coalesced in the 1960s and took a developmental turn in the late 1980s, with important ramifications for stem cell and cancer biology. I use personal interviews and the published record to identify social interactions crucial for scientific success in this episode. This yields a robust account of scientific success in practice, which generalizes to other scientific episodes and approximates normative conceptions of scientific knowledge. I then use this robust account to specify the shared epistemic goal of scientific inquiry. The result corresponds to a classic conception of scientific objectivity: knowledge independent of specifiable groups. An epistemic ideal (scientific objectivity) thus results from explication of social interactions in scientific practice, bridging the problematic gap and resolving the dilemma.