When we contemplate our image in a mirror, biology is definitely involved. - Our Euclidean-space-adapted vision does not deal as well with visually distorted objects. For this reason, we tend to enounter planar mirrors. - Our gravity-adapted vision does not deal as well with objects that are not subject to the gravity we are experiencing. For this reason, we tend to encounter mirrors that preserve the up-down orientation of reflected objects. - When viewing a mirror, we have to face it fairly head-on in order to see our own image. I was going to make a point here, which escapes me now. - Our object-oriented brains perceive reflected images as real objects, subject to same spacial manipulations perceived to apply to natural physical objects. - When comparing two human beings, our face-oriented brains mentally move their images, primarily their faces, to the same location and upright orientation via virtual physical motions. When we do this with a person's natural and mirror images, the plane of reflection becomes the saggital plane of the identified faces, hence we perceive left-right reflection. If we did not perform this mental relocation, we would presumably be more cognizent of the actual front-back reflection in the plane of the mirror.