Mirrors and eyes.

If our eyes were one atop the other, instead of side by, would we percieve mirrors to reflect on an horizontal axis instead of a vertical?

Mirrors don’t reflect in any kind of polarized fashion. They reflect exactly as much left-to-right as they do up-to-down.

The problem is our fault. When we hold a book up to a mirror to read the “mirror writing,” how often do we reverse it vertically? Almost never; instead, we nearly always reverse it horizontally, thus deriving Jabberwocky : ykcowrebbaJ

If our eyes were spaced vertically…the question would still be: how, exactly, do we turn around? If we were very agile, perhaps arboreal, and had the habit of turning upside down, then mirrors would appear to reverse vertically. Since we, as ground-limited bipeds, tend to turn around horizontally, mirrors appear to reverse horizontally.

Experiment: write some words in a marking pen on a piece of transparent plastic. Hold it up to a mirror without reversing it at all. Read the writing through the plastic. You will immediately see…mirrors don’t reverse anything, at all!

We do. The fault, dear Brutus, is not in our mirrors, but in ourselves.

The fault is that we are horizontally symmetrical. Our right hand looks a lot like our left hand, hence we perceive a horizontal flip. If our heads looked like our feet, we would perceive the flip as vertical.

There was a Cecil column on this topic some time ago. I’ll see if I can find it…

I believe that the reflection is ‘back to front’ regardless of our orientation.

Otherwise, if we rotated our heads 90 degrees then everything would change in the manner you suggested.

It is an interesting question, but I believe the answer above makes the most sense.

Exactly, a mirror reverses front and back. Inversion of left and right follows by the definition of left and right.

This has nothing whatsoever to do with how your eyes are aligned or the fact that we are bilaterally symmetrical. People with only one working eye have exactly the same understanding of left and right and it still gets inverted by a mirror.

It has to do with the fact that we find it useful to have the terms “left” and “right”, which are not absolute directions in space. It enables us to describe things, like the direction of our writing or the way to turn a screwdriver. Up and down are fixed by the local direction of gravity.

There is nothing complicated here, it is just a matter of the definition of terms.

Try this and see for yourself: Affix a mirror to your ceiling over your bed. Lie on your back and look straight “ahead” (up) at it. What do you see?

To restate what others have said, but perhaps more accurately: the mirror reverses nothing. What gets reversed is YOUR left and right when you turn around. Imagine taking a picture of yourself and holding it in front of your face; when you turn the picture around to look at it, you reverse right and left. If you turned it over instead, you’d reverse top and bottom. The mirror just reflects – nothing gets turned.