At work I often use the phrase, “Chocolate and peanut butter.” It’s become shorthand for things that people like but that shouldn’t mix: Two great tastes that don’t go great together.

If you grew up in the 80s, you know where the idea comes from, but it takes a little disambiguation, as I’ve inverted the meaning. For those of you deprived of the old Reese’s Peanut Butter Cup ads, Youtube is your salvation:

I like Reese’s Peanut Butter Cups, and I think putting chocolate and peanut butter together is a great idea, but there are some flavors that shouldn’t mix, and “chocolate and peanut butter” is snappier and gets the point across better than “clam chowder and rainbow sherbet.” The phrase usually comes up when people are talking about mixing genres, usually fantasy and science fiction.

Whoa there! If a dozen or more successful mixed-genre properties just leapt to mind, you don’t need to tell me about it. I know that it can work to mix fantasy and sci-fi, and there are many examples that I love. But in the specific case of D&D or Magic the Gathering, the two properties that I work with on a daily basis, inserting science fiction usually doesn’t work out.

Yes you might have had fun playing Expedition to the Barrier Peaks or Tale of the Comet (or god help you, City of the Gods), but if the original Player’s Handbook had laser pistols and space suits in its equipment list, D&D might not be around today. An occasional toe dipped in the water of another genre won’t sink such big ships as D&D and Magic, but a true blending would be bad news. Whenever you blend genres (any two genres), you run the risk of alienating the fans of both and leaving yourself with the tiny audience who love that blend. That smaller audience might be very passionate (I love Firefly! LOVE IT!), but there’s no denying that the mixed-genre property typically fails to gain as much attention as more straight-forward fare—even when the single-genre properties are of poorer quality. (Cleopatra 2525 got a second season. If you’re Cleopatra 2525 fan, don’t even try to tell me it’s as good as Firefly. Just don’t.)

But I digress.

Science and magic don’t mix—or more to the point, they shouldn’t. In this case I’m talking about any property in which some form of magic is explained away with science.

Exhibit A:

Exhibit B:

I rest my case.

Or at least I should be able to leave it at that, but people keep on committing this crime against good sense, so I’ll explain.

People want to believe in magic. It’s part of human nature. Even if you don’t believe in ghosts, leprechauns, or God, part of you wants to believe in them. The world is more wondrous and exciting with magic and powers we don’t understand. It’s why people go to magic shows and cheer instead of hurling things at the magician.

When you tell people that the magic works because of some science, it makes folk examine the idea instead of letting them be swept away by the wonder of it. The whole idea is of course nonsensical and illogical (that’s the point of magic) and so the scientific explanation always falls flat.

In science fiction, you can spread a thin veneer of science over a magical idea (teleportation through transporters, disintegration rays from phasers) and people happily play along. Sure it doesn’t work with today’s technology, but in 2525 or 2266, who knows? But when you explain magic with science, you force people to call bullshit. The magic that people were ready to be swept away by is immediately revealed to be a sham. People know magic does not exist—especially your made up magic that they’re seeing for the first time in a movie or reading about for the first time in a book. It’s like telling kids Santa doesn’t exist while they watch a Christmas special.

Magic is great. Science fiction is great. But they don’t make a great taste when mixed together. Chocolate and peanut butter, people. Chocolate and peanut butter.