Perception: Not Just To See
4 dimensional vision, the ability to see more than what was presented on the physical plane.
To a flat amoeba with two dimensional sight, they could only view objects in one dimension, their lengths. So if a small ball was in their range of view, all they would think to be ahead is a straight line. They would not be able to see its width, nor would they be able fathom its depth. The 3D world would look strange from their point of view, as things would seem like they just appeared within their range of sight, only to disappear without a warning.
The same could be said to humans who existed in the third dimension and possessed eyes that viewed with third dimensional vision. This meant that all we can truly see are in two dimensions, just like the two dimensional amoeba could only see in one dimension.