Today I came up with a wonderful way to explain the aspect of language that I write about in my thesis--except I can't use it in my defense, because the only person in the room who'll know what I'm talking about is my boyfriend, and that's because it's an analogy to Magic: the Gathering.
Here's how casting a spell works in Magic: you declare that you are casting the spell, you tap the amount of mana required to cast the spell, and you show the card representing the spell to your opponent. The spell goes on the stack, giving your opponent an opportunity to respond. If everything goes according to plan, the spell resolves and its effects happen.
The declaration that you are casting a spell is what linguists call a speech act or a performative act. By saying the words, you are doing performing the action the words describe. Other speech acts include requesting, promising, voting, asserting, and apologizing. (These five represent the five categories I sort speech acts into in my thesis. I think, but am not sure, that casting a spell in Magic is most like asserting. It could be like voting.)
All the things that make casting the spell go smoothly--having the card in your hand, having the right amount of mana available to tap, your opponent not countering or redirecting it--are the felicity conditions of the speech act. Different unmet felicity conditions have different effects on how the spell/speech act fails to resolve. If you don't have the card, or don't have the mana, the act can't be performed. The parts you've tried to do get undone, and you may get a warning from a judge if you're playing in a tournament. If your opponent counters your spell, the spell is cast, but has unintended effects: you and your opponent have each moved one card from your hand to your graveyard. (There are other ways spells can fail, but these are the most common.)
Regular non-game-related speech acts work the same way. If you try to declare two people married, but you aren't presiding over a wedding, either nothing happens or someone gets mad at you. If you make a bet, but no one accepts it, the bet doesn't happen.
These are the basics of what speech acts are and how they work. Hat tip to How to Do Things With Words, a collection of lectures by J.L. Austin published in 1962 in which he figures out all this stuff and more. If you want to know more about my thesis, what I actually do with the speech acts, and what politeness has to do with any of this, I'd appreciate it if you commented on this post or sent me a tweet.