"Well, to build a tier of any kind of magic, you need residue. For natural magic, you give off residue naturally just as a result of normal physical activity, and you have to learn to capture it. Sorcerers get a little bit of spell-like abilities they can use to generate residue, but if you want to be a different kind of arcane caster you have to either build residue through scrolls or have residue given to you by an established caster."

"Do you think I could learn magic, or do you have to be from this universe to do it?"

"Extraplanar entities do magic not from their native planes all the time. I think we have a library that was funded by donations from a wizard who's a Celestial."

"Awesome! What's a celestial? And can I sign up for magic classes if I don't have any of this plane's money?"

"A Celestial is...an Outsider from one of the three planes aligned with Good. This is a university, so in general no, but I bet if you'll agree to a certain level of analysis and experimentation we can work something out, since as far as I know you're the only person from your plane ever to reach this one."

"Being an experimental subject in exchange for room and board and tuition sounds excellent! And once I learn the local language I can probably get a job somewhere as well. What does it mean for a plane to be aligned with Good?"

"Well, uh, in general it just means your alignment on the ethical axis is Good, but in the case of Outsiders it means they have a weird magic thing going on where they can't not have a Good alignment."

"So, uh, I definitely know that goodness and evilness are things and have a pretty good idea of what's good and what's bad, but what exactly do you mean by an alignment on the ethical axis? Are outsiders just unable to do anything they think is morally wrong?"

"Good-aligned outsiders can take evil actions that they sincerely believe to be the alternative to much more evil outcomes; they can't...not care."

"Huh. And then humans and elves and so forth are like they are on my world, with some of them doing the right thing more often than others and some of them caring about it more than others and lots of different opinions on what the right thing to do is in a given situation?"

"Yeah that's pretty much just how people are."

"I am now glad that I landed among psychologically similar beings and not incomprehensible aliens, since now I think about it that was not at all guaranteed."

"Celestials aren't incomprehensible aliens. Even demons aren't, really, although you should definitely be glad you didn't land in any Hell for completely separate reasons."

"If the translation there is at all reasonable, then yes. Um, do people end up in any of these planes when they die on this one?"

"Yeah, why?"

"Um, several reasons--if some people end up in planes it's bad to end up in, that's a problem, and also in my world we have no idea what happens to people after they die. The best guess is that they just stop existing altogether. But one of the other guesses involves something kind of similar to what it sounds like you've got."

"Well, uh...ending up in an evil-affiliated plane isn't a great time, but to avoid that all you have to do is not be evil, so..."

"Is it sufficiently clear what things count as evil that hardly anybody has to worry about it? That's definitely better than the alternative."

"Most things are obvious, but, like, you can check what alignment someone is, and if they get a surprise they can change their behavior."

"You have some way--I assume it's magic?--to determine how ethical someone is? Does it get the same result every time regardless of who's checking? Also now I kind of want somebody to check mine, I'm quite sure I'm not evil by my own standards but it sounds interesting."

"Uh, yeah, what alignment you are is, like, a magical property." 

"That is so weird, as far as I know my home universe doesn't have any opinions on ethics. There's just people judging each other."

"...I mean, murder and terrorizing villages and whatnot are evil no matter where you are, I don't think that can ever be just a matter of judging people..."

"Right, yeah, but there isn't any magic to determine whether, I don't know, killing a kid is more or less evil than killing an old person, or whatever. So people end up disagreeing about it."

"I mean, we don't have precise measurements, we can just tell if something's evil or not. Those are both evil. I guess someone somewhere could do some experiments on how many of each one it takes to push people out of good or neutral brackets but, uh, that'd be pretty evil."