In the field of medical imaging, theory, technique, and rhetoric converge to produce knowledge. Historical taboo and cultural belief in the fragility of life have protected the interior of the human body from the scientist's prying eyes; nevertheless, in the modern period (since about 1540), the production of medical knowledge has depended on the unveiling of physical detail. Recent work in the sociology of science—notably Bruno Latour's concept of the theater of proof—has questioned this epistemology. Latour argues that scientific knowledge can be produced by superimposing data that create an effect of reality. To illuminate traditional strategies for constructing convincing accounts of hidden biological processes, I examine texts by Andreas Vesalius, William Beaumont, and Wilhelm Conrad Röntgen. I then discuss an advertisement for a contemporary medical-imaging device that, by foregrounding the superimposition of diagnostic data, provides a useful counterexample to the constructed objectivity of the earlier texts.