"Okay, doesn't prevent unfair bargains known to both parties to be unfair.  Try telling me that your other shoe is worth twenty thousand gold pieces."  What is the thing with gold around here, Keltham ran across that in the books but it didn't make any sense there either.

"The other shoe is -"

She stops.

"The other shoe is worth -"

"The other shoe is worth.  Twenty thousand.          -"

Hmmm!  "Worth twenty thousand what?"

She looks very frustrated! "I'm just trying to say what you told me! The other shoe is worth....you told me to say the other shoe is worth twenty thousand gold pieces." That works fine. 

"Like Zone of Truth, but first-circle, with the visual indicator it's in place." How would you do that, spells can't usually do disparate things like communicating whether they're in place and also having their primary effect, not at first circle. Some god invested a lot of effort in that.

"Truth spell?  Try two plus two equals four, then two plus two equals five."

"Two plus two equals four. Two plus two equals. ...two plus two might sometimes equal five somewhere."

"Okay, out of context, answer this one honestly:  Do you, in fact, believe that two plus two might sometimes equal five somewhere?"

"Yeah, somewhere, there are lots of worlds and you can do a lot of weird stuff with magic and I haven't encountered any proofs that there are kinds of magic that definitely don't exist or things that no kind of magic could possibly do. ...I don't think you could do it with our kind, though."

"One of us is very deeply confused, and I wish to eternity that I was sure it was you, but let's set aside that topic for later.  Try saying out loud that there's a ninety-nine percent probability your shoe is worth twenty thousand gold, then saying there's a one percent probability your shoe is worth twenty thousand gold."

Keltham has been trying to think quickly about lie detection.  If one tries taking all appearances at face value, some of the things he believes are in conflict with each other, meaning he needs to keep track of separate lines of possibility.

Branch 1:  Keltham actually did summon a completely unknown god to Golarion and its first-circle spells can do things that were not previously possible... no, it's not that, Carissa said there was such a thing as a Zone of Truth spell.

So, branch 2:  Truthtelling spells are known.  They should be incredibly useful.  If they're first-circle cleric spells, they should be in first-circle cleric books.  This whole planet does not look like a whole planet should, if it is very easy for people on that whole planet to trust each other - even if it requires paying a cleric, it should still have a huge effect.

Branch 2.1, maybe the clerics themselves are just not trustworthy?

Branch 2.2, the spell is very easy to fool.  Like by using Carissa's illusion spell to fake that symbol, even if it doesn't go up or disappears.  Depending on what kind of illusion-piercing utilities exist, and how much those cost, and whether you can counter illusion-piercing by paying even larger costs.

Branch 2.3, they're lying to him about what the spell really does, because it would be very useful to criminal!mastermind!Cheliax if Keltham believes he has an unstoppable truth-compelling spell, while actually it just inclines people to slightly more honesty or even does some entirely separate thing they don't want him to know.

Branch 2.4, the spell works perfectly and unstoppably and Keltham is wrong about what effects a truth spell should have on a society.

"There's a ninety-nine percent probability that my shoe is worth -" 

"There's a one percent probability that my shoe is worth -"

Imperfect evidence is still evidence, and there are possible worlds where the obvious test will yield useful results.  They may not be ready to defeat truthtelling spells right now.

"Okay, let's work under the assumption it's an honesty spell.  Does not prevent attempts at deception, does not enforce objective truth, you just can't say things you know to be false.  Um -"

Keltham isn't comfortable with this.

...people's lives and money are at stake, somewhere in the background, he really should do it anyways.

"I'm very sorry about even asking this, but I'm in very weird circumstances where I know very little about this world, so - are you alright with me asking one or two questions about this whole situation, as it is known to you, while you're still under a truth spell and there's been very little time for anybody to prepare for that?  I'll try to keep my questions narrow.  I wish I could promise that I won't update on anything if you refuse but, realistically, I can't actually promise that."

"Yes, of course," she says immediately. 

The people presumably monitoring this situation had better not need that much time to prepare a Dispel Magic and an illusion, she thinks and if they have fucked that up then clearly being on the Material Plane just isn't for them.

That was a weirdly fast response for somebody asked if she and her government are okay with her being interrogated under truth-detection, and strongly suggests that Unnamed Female Chelian #7 had thought through her answer to that question before Keltham asked it.  Did they know what spells he had already, with the apparent experiment a sham?  Wouldn't she be trying to conceal her speed of thought in that case, with a fake delay?

Keltham thinks of another obvious fillip to this test, but he's not sure he can ask questions and do that part at the same time - Carissa said it required concentration to use the spell he's thinking of.  He'll save it for last.

"Question one," Keltham says, "has your collective presentation of this entire situation and world, as far as you know what I've gotten, been roughly honest?"

"- I don't think I've told you anything except about magic. Everything I told you was true and not misleading or anything." That should be enough time for an illusion and a Dispel. "I don't know of anyone else having told you anything untrue or misleading either. I ...am not entirely sure I understand the question as phrased but I think yes, we have been honest?"

Elias Abarco has a problem. The problem is that Keltham is presumably thinking he'll use Detect Magic to check whether his enchantment's still in place and that will totally work, it'll show an illusion not an enchantment and if Keltham can read it, game's up - and even if he can't, he can learn how in the future, they can't teach him illusion and enchantment swapped, forever - he can put the girl under another enchantment easily enough but the illusion'll still be there - what he needs is Greater Magic Aura, which can put the girl under the exact right apparent magical signature, but he didn't prep that and doesn't have time now -

There's got to be a scroll of it somewhere. 

Elias Abarco vanishes. This is noticeable to about half the assembled persons but they all have good poker faces.

Well, the symbol's still there.  Though it could be an illusion now.  Though some of that response seemed - suspiciously specific? - and she wouldn't need to do that if they were spoofing the spell by any number of magical means - but then she could be giving suspiciously narrow answers just to make him believe that - alternatively, in worlds where she's being honest, maybe it'd help if Keltham showed her that he is going to be reasonable in what kind of answers he expects?

"To the best of your knowledge, and your best guesses where you do not know, is the Chelian government concealing any major facts from me not relating to its internal security measures and standardly classified secrets, or secrets meant to ensure my own safety or the safety of other people of Golarion from me, or knowledge that is intrinsically harmful or intrinsically vastly dangerous?"

"I don't think so? I am pretty sure the Chelish government is not concealing any things from you that I am allowed to know. I think the things I am not allowed to know are all in the categories you mentioned - security measures, secrets meant to ensure peoples' safety, knowledge that's harmful or dangerous. ...probably there are some government secrets that are just embarrassing rather than properly critical to national security? I don't know of any, just, that's what I would expect, and I'd expect it to also be true of all other countries."

Why do the Chelish allow their version of Governance to keep secrets just because they're embarrassing - no, he shouldn't ask that right now.

Darn it, he should've asked her if the government was keeping any secrets, first, without the qualifiers.  To see if she would've danced around that one, or maybe implausibly answered 'No', and then Keltham would've had a high probability on the test results being faked in that branch of reality -

Keltham really wishes he'd LARPed this at least once before trying to do it in real life.

"To your best knowledge and best guess, if somebody purportedly representing Cheliax signs an agreement with me about credit for information given, future equity shares in industrialization projects, or similar matters, what's the probability Cheliax goes back on their word as represented by the person purported to me to represent the Chelish government?  Excluding scenarios where I would obviously agree in retrospect that the agreement should be broken as a matter of drastic urgency because otherwise Rovagug gets loose or whatever."

"Uh, very low? ....I think I can't give you a number without having a specific person in mind. If a person cheats you on a contract you can take that to the courts and they'd side with you, under the circumstances described. I cannot really imagine a situation where someone tries to do that and the contract is on your side but the courts decide to let them, that's basically just....abandoning being a Lawful country - Asmodeus is the god of contracts, He wouldn't approve of that -"

Keltham tries to think quickly about what he should be asking about here.  They don't actually know how to be Lawful; this much is obvious at a glance.  So in their distorted conception - "Am I liable to need to negotiate incredibly carefully, because somebody's gonna eat my abdominal fat* if I forget to insert a clause saying they can't do that?"

(*) A Baseline idiom roughly equivalent to "skin me in a deal".

"I think it's recommended to read contracts really carefully and if you can afford it with intelligence enhancement up? I, uh, even if you fail to word something carefully obviously there's also the thing where if you feel like we're being bad trade partners you can deal with someone else in future? But I would definitely not avoid spelling something out on the assumption that we think the same things are being reasonable."

"Sorry for demanding that you spell it out, but on your best knowledge and best guess, how much does the Chelian version of Governance reliably care about not looking like they're bad trade partners when dealing with somebody like me?  Are they liable to, I dunno, yoink all the gains from trade with a clever contract term and then classify the whole thing a secret so that nobody knows about it?"  That kind of thing being allowed to governments is still weirding Keltham out, he's only been here a day and that's not nearly enough time to get used to the idea of governments behaving like the governments around here.

It's the Chelish government but she wouldn't dream of correcting him about this. "I don't think they're likely to do that? If they did you'd probably leave, right, and do this work somewhere else, and they really want you to do it here. If there was some way they could, uh, invalidating your will when you died of old age because it had a loophole, and requisition your money then, maybe they'd do that? Because all that'd change if people knew about it is that they'd try to write their wills without loopholes? I'm not a contract lawyer, though, and you probably want one."

Keltham is trying to think quickly because he doesn't know how long the spell lasts and - what else should he ask, he doesn't know -

Well, there's always going meta.

"Say what you think is the question that I would most, from my own perspective, want you to answer under truth spell, with your statement including your stated belief that it's what I'd most want to ask."