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This might be a little off topic, but I hear that some people claim that they can imagine 4-dimensional objects. I wonder how this can be since our universe only has three physical dimensions - is it really possible to imagine these things and do these people have any proof? I myself find it impossible to imagine anything but projections of these objects onto 3-dimensions. I do not know how people can imagine a Four-dimensional object. We live in three dimensions, and it is difficult to imagine another "direction" that is perpendicular to our existing dimensions. Perhaps people with special imaginations can do it.

This seems analogous to color vision. Humans usually see three primary colors, and the brain is able to "see" the full spectrum of colors from these primaries. Some creatures, like insects, have a fourth primary color receptor. They might "see" colors that humans cannot imagine, or at least I cannot imagine.