The whole time I've been reading Flatland I've tried to picture what a comparable version of it would be for a 4 dimensional being visiting a 3 dimensional being. I've been picturing 4d vision as being able to see the entire surface area of a 3d object all at once, but now I think that might be comparable to a 2d person thinking that 3d vision only means being able to see all of the exterior edges of an object at once, without picturing any of the planes that connect the lines. I think a more accurate description of 4d vision might involve being able to see *every single* cross-section of a 3d object all at once, from *every possible* angle at once, as one coherent visual whole. And the idea of someone being able to see every single cross-section of a body all at once, brain and guts and everything, laid out all together as if on a flat plane, is a horrifying mental image