So I said, mirrors allow us to see the physicality of our character. However, it's still a mirrored image, reversed from left to right. In this sense, they do not allow for a perfect image of ourselves. This is, in my opinion, irrelevant. The mirror still allows for essentially all that we would need in seeing our own face.
The issue of the mirror, however, is that which is presented by Mr. David Lynch so appropriately in the finale of Twin Peaks.

Here, as I fear, as it is clear in the mirror, Agent Dale Cooper is not as he appears. This is the problem with mirrors. Vanity is okay--we all love looking at ourselves. However, the mirror speaks on other levels. The mirror makes "important connections with the other realm. It has always opened onto the other place: the reversed world of the dead." (Rickels, 13) Lynch knows this, and uses the idea quite well.
If I were to attempt to suggest meanings for all of the bizarre locations, wacky symbols, and seemingly apparent "metaphors" in Twin Peaks (which is something I'd rather not do, but to make a point I will anyway), then I would probably assume the locale of the "Black Lodge" or the "Red Room" as a place where certain dead people go--be it a version of Hell, or the Underworld, or perhaps a bewildered limbo-Valhalla ("This is the...waiting room..."). Now considering that this "Black Lodge" is accessible to living man, and escapable by the spirits/beings that inhabit it, we must consider the gateways between the worlds that are presented.
Let me first examine the pool of "scorched engine oil," which marks the portal to the "black lodge." Is this not a reflective pool? A dark mirror of sorts? And is it not reminiscent of Narcissus' demise? Let Dale enter the lodge, encountering this pool--he does not return the same. He is possessed by the spirit BOB! And there, upon approaching the mirror in the final shot, he is not reflected as Dale, but as Bob himself.
This is the problem. The rule of the mirror is quite strict. If you don't see yourself in the mirror, something's terribly wrong. It seems the general understanding is that you're not quite alive if you can't see your reflection as it's *supposed* to be.
Why is this not the darkest fear of people? Why are so many afraid of the dark, or of what is hidden in the dark, when we can rely on our other senses to protect us within it? At least we have some defense there. But the mirror--imagine seeing the wrong thing! This is a terribly disturbing thought. Consider the vampire--consider seeing a reflection of only the space behind you.
In this way, the mirror is strict. It is not a machine--if we witness an incorrect reflection, then we cannot assume the mirror is simply "broken." Moreover, it cannot be held accountable for failure to provide a reflection. According to logical thought, this might suggest that anything we observe in the mirrored world is and must be true, or at least presented to us in a manner depicting truth. The mirror would not show Dale an image of Bob if Bob was not somehow, in truth, inhabiting (or at least strongly related to) Dale--all because the mirror does not lie.
A truth-teller. If there were an antonym of "liar," then the mirror would make a fine example.
Let's consider this "broken mirror" idea. Assuming we take it in the non-almost-literal sense of not functioning correctly (i.e. showing us the wrong reflection or none at all), then it is apparent that whatever we might be sensing here in the non-mirrored world is less than whole--there's more than there seems. Assuming we consider a "broken mirror" to be one that is physically broken, or shattered, or lying in pieces, then we are left only with several small reflectors--dozens of shards, all with the potential to show us something terribly frightening--and the mirror is only just deconstructed, broken into smaller parts that are comparably important. So we are at a loss for protection from this mirror world. Smashing the mirror would only make things more perceivable--power in numbers.
So is this what Pete Townshend used the mirror metaphor for in his opus Tommy, from which we hear the story of a boy set deaf, dumb, and blind as the result of certain childhood trauma, only to be cured later in his life upon smashing a mirror? Surely the mirror is a great signifier of a connection between two worlds, just like Rickels suggests, but I never quite understood the significance of "smashing" the mirror, especially in its relation to the curing of the boy, Tommy. I held an opinion for some time that Tommy must have been in the "dream world," the "silent vibration land," (Townshend), and by smashing the mirror he metaphorically transports himself to the waking life by means of breaking down the barrier between the two.
This connects quite nicely. If we take Rickels' idea that a mirror is a connection between two worlds, along with Townshend's--that a "broken mirror" is an open gateway--combined with the thought that a truly shattered mirror means higher quantity of truth-telling reflection, and mix those up with the idea of a "broken mirror" being a non-functioning one, then it is obvious that the broken mirror cannot be, in any sense of being "broken," telling a lie. This is because if you look upon a mirror, and see something that's not right, you cannot fix the mirror. Moreover, if you break the mirror, you will only wind up with dozens of incorrect reflections.
Now,
Say you've got a magical, non-functional mirror. Maybe you want to try some other mirrors along side it to see if they'll provide a different result. And say they don't. Say they all show something wrong. Well then you're obviously witnessing a popular perception of you in the mirrored world, and it can be understood as a truth that you are more (or perhaps less) than you think you are. Say the other mirrors do present you accurately, and you actually have a dysfunctional mirror after all. Well then now you've got magic, simply put, and turns out you can safely assume there is more in the world than you had thought! Like that, a non-functional mirror is no longer a non-functional mirror, but rather an obvious and easily-read symbol of some certain truth--because that mirror will never reflect you, no matter what you do to it, unless, I suppose, it just simply *feels like it*...
And there! If a mirror can *feel like* something, then that implies there is another world of perception and thought. If it *feels like* something, then suddenly we know there is a world unfamiliar to us, a world indistinguishable by our senses--one that is inside, or maybe around, or maybe behind (oh yeah, we can't distinguish it...)--well it would have something to do with the mirror, albeit sensory or not.
As a brief change of subject: One time, or perhaps dozens of times, English teachers at my high school would tell me not to begin a concluding paragraph with the words "In Conclusion..." They also told me not to bring up new ideas in the concluding paragraph. But goddammit, how is one supposed to leave someone thinking if they conclude with what they've been writing about the entire time?
In conclusion, vampires cannot be seen in mirrors because it is simply just as feasible for a vampire to exist as for a non-functioning mirror to do the same--thus the mirror is representative of a world separate to the one our senses perceive, representative of a world of ghosts that leave their coffins at night to suck the blood of virgins and other people and stuff, representative of a world where vampires actually exist. Vampires can't exist in a world where mirrors reflect them, otherwise they wouldn't really be vampires would they? They'd be some other blood-thirstin' sucka. We gotta have one magic, to have the other magic...
Oh no:

No, that's just a vampire on a mirror...
Oh no, wait:

Damn. Well that's rough for you guys, Hollywood. Edward... in a mirror.
Now I'm confused.
Maybe I'll post more on this thought process another time...
-CS