The Eyeliner Principle is simple. For decades, eyeliner on men has meant Evil in science fiction, adventure, and action movies and TV shows. (On women, eye makeup has little significance. I would say on women it means the character is awake, but we all know that Hollywomen sleep perfectly made up, and seeing them without eye makeup is about as common as seeing them in bras that don’t match their underwear.) Pirates of the Caribbean broke new ground using eyeliner for the merely morally ambivalent.

Now, you could probably come up with several cultural explanations for this: eye makeup is associated with women, so men with eye makeup are coded as effeminate and therefore transgressive, flawed. Or perhaps it’s playing on white audience’s xenophobia – certainly some eyelinered villains, like Emperor Ming in Flash Gordon, play on tropes of the dangerous, exotic Other. Maybe it’s a mish-mash of the two. Whatever the origins, it’s a pretty good bet when you see a guy in eyeliner in a mainstream piece of media, you shouldn’t trust him.

I bring this up because it isn’t just a handy way of tagging baddies like the fiancé in Titanic. It allows the omniscient viewing public to differentiate good male characters from their evil twins, clones, doppelgangers, possessed or de-souled counterparts. This incurs no plot damage, since the other characters always seem to be ignorant of the Eyeliner Principle (they seem to be slow to catch on about leather pants, too). This holds true everywhere from Young Hercules (Yes, I’ve watched that. Hercules isn’t the only one that was young once) to Star Trek. Which is really the reason I brought this up*. It’s important that you all know that Captain Kirk with eyeliner is evil. Seriously, if you ever see William Shatner wearing eyeliner, run…and thank me later.

*More on Evil Kirk coming soon!