 Even with Helmholtz available, Reichenbach is concerned to dispute further the very idea that Euclidean geometry has a privileged status in mathematical visualization that indicates some intrinsic limitation of thought. If humans had somehow been transported to a non-Euclidean world, he says, they would have non-Euclidean visualizations—surely a puzzling counterfactual. The very idea that “pure visualization” has some normative content is a mistake, he argues: “the normative function of visualization is not of visual but of logical origin.” (p. 91). We do not presume to know just what Reichenbach meant here, but for a plausible elucidation one might turn to recent philosophical work on the logical relations implicit in geometrical diagrams. 