Hume's Guillotine sets up an ethical regress problem

[Coffee Jesus]

I don't see how moral realism is that difficult.

Hume's Guillotine (the is-ought problem) is the problem of justifying an evaluative statement with purely descriptive premises. The idea is that an evaluative claim would be objectively true if it could be piggy-backed on an objectively true descriptive claim, and then it could be used as the premise for other evaluative claims.

I thought Hume's Guillotine was this insurmountable problem until I looked at it as a regress problem. If the only justification for an evaluative claim can be other evaluative claims, then where does this regress of moral justification end? As it turns out, descriptive claims encounter the same sort of regress problem. There are different responses to the epistemological regress problem: foundationalism, coherentism, intuitionism, pragmatism...

I think qualia (mental experiences) provide foundations for both descriptive and evaluative frameworks. Qualia are indefinable yet undeniable. Most or all epistemological theories assume qualia to be a reliable source of information. Finally, certain qualia are intrinsically good or bad.

[MindForgedManacle]

Not sure what you mean. Hume's is-ought distinction merely points out that you cannot go directly from a descriptive statement to an evaluative statement... without some means of showing why they follow. That is, one must argue for it. It was never meant to be seen as insurmountable. In fact, Hume saw it's real use as a good way to beat down any religious moral system.

So, I could cross the is-ought gap fairly straightforwardly via goal-directedness. For example:

If I want to win a race, then I ought to run the fastest.

[Coffee Jesus]

So, I could cross the is-ought gap fairly straightforwardly via goal-directedness. For example:

If I want to win a race, then I ought to run the fastest.

Isn't that still subjective? Whether you ought to run fast will depend on who is asked and what they want.

Regress problem:
https://en.wikipedia.org/wiki/Regress_problem

[MindForgedManacle]

Exactly. This isn't a problem, because you can't argue people into valuing something without appealing to something they already value. Value is by definition subjective, and could never be otherwise. The correct response to Hume's Guillotine is not to abandon moral realism, but to abandon derivation of values purely from facts.

[Coffee Jesus]

Value is by definition subjective, and could never be otherwise.

I disagree. I think evaluative statements often express qualia—such as the pain of being burned or the pleasure of intercourse—just like the word "bright" can be used to express a quale.

[MindForgedManacle]

...? Aren't qualia by definition subjective? (i.e. my feeling of perceiving redness itself, etc.) Even if they refer to something that is in a sense objectively real, they are about subjective experience, or in other cases, desire. Goal-directedness plays off this, by merely going from one's values and desires to that which will lead one to fulfill it.

[Coffee Jesus]

The quale word doesn't just express that instance of that quale, it expresses every instance of that quale, so my statement "the sensation of burning is painful" is objectively true as long as the subject experiences burning as I do.

We can infer what other people will perceive as painful or pleasurable before they tell us. This means they are identifying pain and pleasure in the same way as we. They have the same qualia.

[Jackalope]

We can infer what other people will perceive as painful or pleasurable before they tell us. This means they are identifying pain and pleasure in the same way as we. They have the same qualia.

Can we? I know a few masochists who might disagree with that claim.

[Coffee Jesus]

We can infer accurately enough. Some people might experience things a little differently, but no drastic differences.

-edit-
Brain scans would probably be the best method of inference.