Do physicists believe that general relativity is true, and that electrons and phonons exist, and if so, in what sense? To what extent does the spectrum of positions among physicists correspond to philosophical positions like scientific realism, instrumentalism, or perspectivism? Does agreement with these positions correlate with demographic factors, and are realist physicists more likely to support research projects purely aimed at increasing knowledge? We conducted a questionnaire study to scrutinize the philosophical stances of physicists. We received responses from 384 (...) physicists and 151 philosophers. Our main findings are (1) On average, physicists tend toward scientific realism, and slightly more so than philosophers of science. (2) Physicists can be clustered into five groups. Three show variants of scientific realism, one is instrumentalist, and one seems undecided or incoherent. (3) Agreement with realism weakly correlates with approval of building a bigger particle collider. (4) Agreement with realism weakly correlates with the seniority of physicists. (5) We did not find correlations with other factors, such as whether physicists focus on theoretical or experimental research and whether they engage with applied or basic research. (shrink)