The confusion ultimately comes from a nebulous understanding of "flip". This is what we mean when we say our mirror image is flipped: We imagine the mirror repr

The confusion ultimately comes from a nebulous understanding of "flip". This is what we mean when we say our mirror image is flipped: We imagine the mirror represents an extension of our normal 3D world and rotate our body around the z-axis until our head and legs line up. That's we interact with our 3d world: we translate and rotate objects. However, this isn't the only way to "flip" (i.e. rotate back). It seems like the only way because it is the only way to rotate the mirror image onto something that aligns with the non-mirror reality. The head must align with the head and the legs must align with the legs, and there is only one rotation that makes it work. But now imagine you had some sort of isle of man flag [1] type body. That is, your arms remain, but your feet and your head turn into an arm. For lack of better term, call your "head-arm" upper-handed and call you "leg-arm" lower-handed. Now when you look at your freakish mirror image, there are TWO ways you can rotate your the mirror image to correspond in some way with your body. You can rotate as usual around the z-axis, but you can also rotate around the y-axis. In that case, your left and right arms are not flipped, but your upper-arm and lower-arm are flipped. That is, the whole confusion occurs because humans are symmetric in one dimension and non-symmetric in another. We are: ==Y== X=O=X ==Z== As opposed to ==Y== X=O=X ==Y== [1] https://en.wikipedia.org/wiki/Flag_of_the_Isle_of_Man https://en.wikipedia.org/wiki/Flag_of_the_Isle_of_Man