This article compares investigations of the process of vision that were made in early nineteenth-century Britain and the German lands. It is argued that vision studies differed significantly east and west of the North Sea. Most of the German investigators had a medical background and many of them had a firm grasp of contemporary philosophy. In contrast, the British studies on vision emerged from the context of optics. This difference manifested itself in the conceptual tools for the analysis of vision, deception and illusion and shaped the experiments on visual phenomena that were carried out. Nevertheless, both in Britain and in the German lands vision studies were driven by the same impetus, by epistemological concerns with the nature and reliability of knowledge acquisition in experience. The general epistemological conclusions drawn from researches on vision and deception were optimistic. Precisely because mechanisms of deception and illusion could be uncovered, the possibility of acquiring empirical knowledge could be secured.