The measurement of angels. Images of pure mind as a matter of science in the 19th century

During 19th century there was a migration of angels from their usual places in religion, art, and literature into the field of natural sciences. In works of Carus, Fechner and Exner, angels became objects of physiology, comparative anatomy, and astronomy. Although traditionally angels are considered as images or materialisations of pure mind, respectively of metaphysical/transcendental elements, such empirical methods of dealing with heavenly creatures have several precursors in history. This article discusses the traces of angels within the history of knowledge and arts as a specific dialectic of secularisation, focusing on the metamorphosis of heavenly creatures into representatives of the miraculous in 18th century aesthetics. Concerning the issue of representation, the article analyses the disappearance of materiality of painting through techniques of reproduction as prerequisites to transform the angels into objects of experimental research in 19th century sciences. As a result, the angels may be interpreted as symptoms of the problem of visualisation within a context where sciences have to address the boundaries of positivistic methods, for instance as a historical example for the epistemological problems of brain imaging.