Michael Evans’ article, “Defining the public, defining sociology: hybrid science—public relations and boundary-work in early American sociology” has been published in Public Understanding of Science. This paper examines how scientific disciplines define their boundaries by defining the publics with whom they engage. The case study is an episode in the development of early American sociology. In response to the dual challenge of credibility set up by the conflict between religious Baconian science and secular positivist science, key actors engaged in specific strategies of boundary-work to create their desired “sociological public”—a hybrid form of science—public relations that appealed to hostile university scientists while excluding a supportive religious audience from participation in the production of scientific knowledge. Using this case, Michael offers two specific insights. First he illustrates how, in the pursuit of scientific credibility, actors engage in boundary-work to differentiate audiences, not just practitioners. Such defining of publics is constitutive of scientific disciplines in their formative stage. Second, he demonstrates how audience boundaries can be redefined through the capture of existing boundary objects. Specifically, the removal of informational content in key boundary objects creates durable boundaries that are difficult to overcome.