In the spring of 1893, the Austrian writer and critic Hermann Bahr began interviewing various people on antisemitism, a subject of heated discussion in the European feuilleton around 1900. “Once again, I am travelling the world sounding out people’s opinions and listening to what they have to say,” he wrote in his introduction to a series of articles on that issue that appeared in the feuilleton of the Deutsche Zeitung between March and September 1893. A year later, the Berlin publishing house S. Fischer turned Bahr’s articles into a book. Bahr conducted a total of thirty-eight interviews with prominent personages, such as August Bebel, Theodor Mommsen, Ernst Haeckel, Henrik Ibsen and Jules Simon. Bahr did not focus on the arguments in favour or against antisemitism. Instead, he set out explicitly to investigate the sentiments, perceptions and opinions on this topic within the cultured classes. Yet, as I will show in this article, Bahr tried to capture not only the “sentiments” [Empfindungen] aired by his interviewees, but also the settings and interiors in which the interviews took place. I argue that these descriptions of physical space served Bahr as authentication, as a three-dimensional certificate for the “facts of opinion” [Meinungstatsachen] he recorded.