"An Oath?"

"People... say... vows? Usually? Unless they're doing it valley style or common consensus?"

"...we are having some kind of deep translation issue osanwë's not sufficient for. What happens when you make a vow?"

"Then if you don't do the vowed thing people who know you were supposed to can call you on it and trust you less?"

"Oh. We cannot break our word."

Blink. "That sounds kind of terrible. I mean, useful, maybe, but kind of terrible."

"I find it useful more than terrible, but perhaps under some conditions it would be."

"It just seems really susceptible to oaths made without all salient information, or worded badly, or way too far in advance, stuff like that. Maybe you're all really really careful."

"Most people never use oaths to commit themselves to future courses of action, just for trustworthiness. If the stakes are high enough it is sometimes worth committing yourself to certain reactions to actions by others - that sort of thing has to be worded very carefully, or sworn before someone who can release you."

"Oh, you can be released?"

"If you swear before a Vala then that Vala can release you. If you swear before Eru then you're rather stuck; he does not make appearances."

"And they work for trustworthiness, like, swearing that you really did a thing? What happens if you try to do that falsely - or mistakenly, like, you're swearing you told the truth all yesterday but forgot some trivial fib?"

"That'd be fine; swearing something is done or is true is swearing that it's so to the best of your knowledge, and that you're not misrepresenting the state of your knowledge."

"Okay, that sounds much less horrifyingly unsafe."

"If you tried to swear that you'd told the truth and you knew you hadn't, it also just - wouldn't happen, you couldn't say it."

"I could. ...Unless local rules have been imposed on me by my arrival, oh dear."

"I'd probably test it immediately but I am told I am too curious."

"Is swearing an oath the sort of thing I could do by accident, because if it isn't I might just wait for Valar to show up in a few days and see if they know."

"If you are the type of person who'd get angry and say things like 'I swear I'll kill you' or something - oaths do understand the use-mention distinction, what I just did was safe - then you could do it by accident. That's a valid oath."

"I am not usually that sort of person but I don't want to bet anybody's life or more likely possessions-or-something on it. Would it be a safe test to say something false and then swear that I just told the truth, if I can do that?"

"Yes. If I tried to do that I'd find I couldn't actually swear I'd just told the truth. I would not explode or be in horrible pain."

"Good, I hate exploding and being in horrible pain! Ummm... strawberries are blue. I swear that I have just spoken the truth."

"Looks like Oaths are not a feature of our world but of our nature," Fëanor says brightly. "Interesting. And good, because if you're not in the habit of watching your words it'd be inconvenient to have them suddenly start binding you."

"So inconvenient! I mean, I do make a habit of keeping promises meant seriously but I can get sarcastic and I'm not sure how the use-mention distinction border is drawn when magic is doing the drawing."

"Indeed. I would try to enlighten you but as a child I got in lots of trouble for experimenting."