The introduction deals with two main issues: First, it focuses on the question why a history of scientific concepts should not be limited to the analysis of scientific texts alone. Secondly, it shows how the history of the reflex concept gains from looking at various fields such as art, literature and brain research. The crucial role the reflex played in 19th and 20th century and the different meanings it adopted allowed us to conclude with Bruno Latour that the distinction between art and science is in itself historical. Thus, the distinction proves to be of little use for the historiography of complex concepts such as the reflex which rarely appear to be purely scientific.