A putative mechanic for Battle Librarians of Gnosi, a hypothetical tabletop. It was originally going to be a Dogs in the Vineyard hack, but this mechanic would work better for a Dungeon World hack or something, so you wouldn't know if your theory was correct or not when you propose it. Inspired by the Science, Faith, and Sorcery XP action from Chuubo's.
Once per scene, you may propose a theory about an unfamiliar element of your environment. This could be about the behavior or abilities of a creature you encounter, the properties of a mystic phenomenon present in a particular location, the powers of a magical item, or something else. Then, devise a test for your theory. This should involve at least a little cost and/or risk, like a round of combat or a risk of provoking an enemy or breaking something. Your theory can be something that provides a benefit if true (morgwolves are easily tamed by feeding them carrots) or something that's just for the sake of science (a glowstone will explode if I throw it in the campfire). Roll science! (Or whatever.) On success, your test fits your theory, possibly providing a situation benefit either because of its useful result or because of the joy of science. On a miss, things don't go as you expect, with consequences ranging from just the cost or risk mentioned above to unexpected Bad Stuff as a GM move.
Either way, at least you learned something! Get an XP (or a dot or something) representing what you learned. You are encouraged to write a sentence or two describing your discovery and add it to your expedition's log, to be of course enshrined in the Archives at Gnosi as a record of you expedition and for the benefit of future scholars.
On the surface, it's basically Fate's declaration system, but I like it focusing specifically on theory-testing rather than a way to get something to tag for an advantage. You're not doing it for a +2, you're doing it because in the middle of a fight with goblins is the perfect time to determine whether goblins are allergic to cheese. Any battle librarian could tell you that! I think how well it'd work in practice would depend a good amount on the XP/dot/whatever mechanic. Also, this makes me feel like Battle Librarians wants the stats list to be something like Science, Lore, Observation, Rhetoric, and Discipline. Because you can't have too many mental stats, right?