1 Adam: Is it true that vampires don’t show reflections in a mirror?
1 Shop owner: Da.
2 Adam: So is that because mirrors reflect the soul and they don’t have souls? Or is it the purity of silver that destroys the vampire’s image?
3 Shop owner: Could not say vhy it happens.
3 Adam: There’s another myth we need to test, Jamie!
4 Shop owner: You need silver mirror and dielectric coated pyrolytic glass mirror. You got high credit card limit?

I've known for a long time that vampires are not supposed to cast reflections in mirrors. I wondered about the reason for this, and made the mistake of doing an Internet search...

Needless to say, a lot of nerds have spent a lot of time arguing about this.

The reason that seems best supported by the traditional literature is that mirrors are supposed to reflect the soul. Vampires, being unnatural undead creatures, have no souls. Therefore a mirror cannot show their image. As a magical/occult explanation, this works fine. But of course Internet nerds are not happy leaving it there. The sort of people who think about this^[1] raise the question of why then a mirror reflects inanimate objects, like rocks or bottles. One possible implication is that rocks and bottles have souls - which begins to sound like various forms of animism, in which the world is dense with spirits and all natural things could be said to have souls. Another way out of this conundrum is to suppose that it's not merely the absence of a soul that a mirror objects to, but a combination of some form of unnaturalness with lacking a soul. So a rock is a natural object and gets a free pass from the mirror, despite not having a soul, but the vampire raises a flag and gets a full body cavity search and winds up being rejected.

Of course, accepting the existence of both vampires and souls on faith and then going to town on hyper-reductionist scientific arguments to try to justify some aspect of their purported properties is building a towering edifice on a foundation of quicksand, but whatever.

Another popular theory which seems to have gained some traction is that silver is a pure, heavenly metal, and it rejects the existence of vampires. Putting aside the fact that this seems to be borrowed from werewolf mythology and doesn't come up in classical vampire stories at all^[2], the idea is that the image of the vampire hits a mirror (being a sheet of glass coated with silver) and the mirror burns away the image, and so it is not reflected. People supporting this theory cite various stories of vampires being burnt by silver objects - but again a bit of searching turns up that this was never an aspect of vampire lore before its appearance in the 1960s American vampire soap opera series Dark Shadows, in which it is stated that being shot through the heart (specifically) with a silver bullet will kill a vampire, and in the series' 2012 comedy movie revival flop in which the very touch of silver would burn a vampire's flesh.

Putting aside the fact that this silver theory is shot with holes already, it raises even more questions. Does a mirror made of materials other than silver show a vampire's reflection or not? Which is the point being explored in today's comic.

The silver theory fans also point out that this provided a neat (pseudo-physical) explanation for the idea that vampires also don't show up in photographs. The soul theory of course can just say that photographs capture the soul - an idea with plenty of antecedents - and that therefore a photograph cannot show a vampire. But for the silver theory, there is the convenient fact that photographic film works by the interaction of light with chemicals on glass plates or film. And the main chemicals required to capture a photographic image are silver halides (silver bromide or silver chloride). And so the image of a vampire passes through the camera lens, hits the glass/film, and is burnt away by the silver particles on the photographic plate.

All very neat. Until you ask if it's possible to photograph a vampire with a digital camera, which doesn't use silver halide chemicals. Here the silver fans double down and say, well obviously yes, you can photograph a vampire with a digital camera. The soul theory might differ. So I guess that's another way for the Mythbusters to test what sort of vampire myth they're dealing with.

Another intriguing (for want of a better word) idea I ran across while digging into this particular rabbit hole, is the notion that vampires don't reflect in mirrors because they are transparent. Light passes through them, so the mirror reflects whatever is behind the vampire, rather than showing the vampire itself. This... doesn't address the question of how anyone can see vampires at all in that case - the comments I found just blithely ignored that bit.

In conclusion, it's difficult to say that vampires violate just one law of nature, and then expect everything else about them to be explicable by known science. Once you start with a magical premise, you kind of just have to accept that they work the way they do because they're not of this world, rather than try to figure out how physics allows it to happen. (Not to say that discussing this stuff isn't fun!)

[1] Admittedly I'm one of them, as evidenced by this annotation.

[2] I found several assertions that vampires' vulnerability to silver has origins in Greek mythology, and specifically stemming from an incident with Artemis, goddess of the moon. While intriguing, Vampedia^[3] describes this as a "fake" Greek myth, with origins apparently no earlier than the 19th century.

[3] Yes, I know. Cool name, huh?