 Ken Manders set out to explode this story with his seminal work “The Euclidean diagram”  (2008 [1995]).  His analysis of Euclid’s diagrammatic proof method reveals that Euclid employs diagrams in a controlled, systematic way. It thus calls into question the common, negative assessment of the rigor of the Elements. Moreover, the specifics of Manders’ analysis suggest that the proofs of the text can be understood to adhere to a formal diagrammatic logic. This was subsequently confirmed by the development of formal diagrammatic systems designed to characterize such a logic. The first of these was FG (presented in Miller  2007),  followed by the system Eu (Mumma  2010).