 Nevertheless, as recognized in the philosophical commentary on Euclid’s geometry from antiquity onward, there are with Euclidean diagrams issues of representational scope to contend with. What is the justification for treating properties of a single geometric diagram as representative of all the configurations in the range of a proof? How can a single diagram prove a general result? Manders’ exact/co-exact distinction provides the basis for a partial answer. The co-exact properties of a diagram can be shared by all geometric configurations in the range of a proof, and so in such cases one is justified in reading off co-exact properties from the diagram. In a proof about triangles for instance, variation among the configurations in the range of the proof is variation of exact properties—e.g., the measure of the triangles’ angles, the ratios between their sides. They all share the same co-exact properties—i.e., they all consists of three bounded linear regions which together define an area.