“Treat nature by the cylinder, the sphere, the cone” — Paul Cezanne to a student. The traditions of art education in European and American art schools are clear: use geometry to create art. But which geometry is most useful? Why aren’t we using the crenallated, mobile geometry of clouds in the summer sky or the dendritic branching of tree limbs and river’s tributaries as our favored models? Why do we rely on obviously abstract concepts like line and shape modeled as perfect square or circles, and then cylinders and spheres? Aren’t these geometrics invented human forms, not actual natural ones? This essay updates and complicates these notions with a more contemporary look at the biology of vision.