The puzzle of mirror reversal: A view from clockland

Why is it that when we view an image in a mirror parallel to the object's front, we are aware of a left-right reversal but not of a top-bottom reversal, though the mirror does not optically discriminate between the two axes? An elaborate exposition of ideas formerly proposed by Navon (1987) is presented. It notes that the real source of the perception of reversal is not the one suggested by naive cause attribution: Whereas the mirror does not discriminate between frontal axes, frontal encounters do. Mirror images thus appear to be reversed along a planar axis - the horizontal one, in our ecology - because they suggest a prototypical frontal encounter, yet deviate from it in a lawful manner. The deviation is due to the fact that, unlike in mirror viewing, in any frontal encounter, homologue intrinsic sides are opposite to each other only along one planar axis. The distinguished axis, namely that particular axis whose homologue poles ARE opposite to each other in a prototypical frontal encounter within a given ecology, would constitute there the mirror-invariant axis. A generalization to other coordinate systems, other encounters and other ecologies follows. Finally, other accounts of the issue are critically reviewed.