Your second answer is the nearest to being right, but I wouldn't put it quite like that.
An alternate answer, that a believer in absolute morality or logic might like, is that logic actually deserves a higher place than Euclidean geometry. Where geometry can be tested and modified wherever the data support a modification, logic can't.
Just to clarify: Here you're talking about Euclidean geometry as an empirical theory of space (or perhaps space-time), as opposed to Euclidean geometry as a branch of mathematics. Here is how 'empirical' and 'mathematical' Euclidean geometry come apart: The latter requires that we make methodological decisions (i) to hold the axioms true come what may and (ii) to refrain from making empirical predictions solely on the basis of our theorems.
I don't think there is any important sense in which logic is 'higher' than Euclidean-geometry-as-mathematics.
No matter how many times our modus ponens does worse than an Appeal to Tradition or Ad Populum in some area of inquiry, we still don't say "ok, alter the rules of logic for this area of inquiry to make Ad Populum the correct method there and Modus Ponens the fallacious method there"
I don't think this makes sense.
What does it mean for modus ponens to "do worse" than something? It might "do badly" in virtue of there not being any relevant statements of the form "A" and "if A then B" lying around. That would hardly make MP "fallacious" though. It might be that by deducing "B" from "A" and "if A then B" we thereby deduce something false. But then either "A" or "if A then B" must have been false (or at least non-true), and it hardly counts against MP that it loses reliability when applied to non-true premises.
(You might want to object to the ("loaded") terminology of "truth" and "falsity", but then it would be up to you to say what it means for MP to be "fallacious".)
Going back to prase's question:
What, in your opinion, makes modus ponens better than appeal to authority, independently of its persuasiveness?
Users of a language have to agree on the meanings of primitive words like 'and', 'if', 'then', or else they're just 'playing a different game'. (If your knights are moving like queens then whatever else you're doing, you're not playing chess.) What makes MP 'reliable' is that its validity is 'built into' the meanings of the words used to express it.
There's nothing 'mystical' about this. It's just that if you want to make complex statements with many subclauses, then you need conventions which dictate how the meaning of the whole statement decomposes into the meanings of the subclauses.
I agree but with some spin control.
It might be that by deducing "B" from "A" and "if A then B" we thereby deduce something false. But then either "A" or "if A then B" must have been false
This is key. I like to say that we play logic with a stacked deck. We've dealt all the aces to a few logical rules. This doesn't mean that logic isn't in some sense absolute, but it removes any whiff of theology that might be suspected to be attached.
...Users of a language have to agree on the meanings of primitive wo
lukeprog gave a list of metaethics questions here:
Most of these questions make no sense to me. I imagine that the moral intuitions in my brain come from a special black box within it, a "morality core" whose outputs I cannot easily change. (Explaining how my "morality core" ended up a certain way is a task for evo psych, not philosophy.) Or I can be more enlightened and adopt Nesov's idea that the "morality core" doesn't exist as a unified device, only as an umbrella name for all the diverse "reasons for action" that my brain can fire. Either perspective can be implemented as a computer program pretty easily, so I don't feel there's any philosophical mystery left over. All we have is factual questions about how people's "morality cores" vary in time and from person to person, how compelling their voices are, finding patterns in their outputs, etc. Can someone explain what problem metaethics is supposed to solve?