Oh, when we stray into using physical analogs for morals!
Hey man, I didn't start the analogy. I agree that it's not super useful, except in that it does illustrate the importance of context.
"Visible" is subjective. Darkness is a human perception of there being insufficient visible light present to inform us about our surroundings. But, what seems like pitch blackness to me is perfectly navigable to my housecat. And there are creatures that can perceive parts of the electromagnetic spectrum that I cannot. And there are people who are profoundly blind, and cannot perceive light at all beyond perhaps the warming of their skin.
Sure - agreed. Darkness is what humans call the absence of visible radiation. To us. A definition that has changed as we have found that there are other ways to detect radiation. Context matters.
From which we either have to conclude that moral relativism is the only way to go, or that perhaps the analogy is not particularly useful because it contains implicit assumptions about morality that have not been established independently.
I
definitely conclude that moral relativism is the only way to go. Well, more precisely, metaethical moral relativism. We need ethics, but there has never been discovered a way to prove that one set of ethics is objectively superior to another. From a MMR perspective, the analogy to the natural sciences is interesting (in fact, vital), because it illustrates a key distinction between moral claims, which are inherently subjective, and naturalistic claims, which are objective to the extent that they are measurable and testable. Most folks who maintain a MMR position, including me, are also naturalists, though a few are general relativists (i.e. believing that
all knowledge claims are subjective).
Well, any definition of one implies the other as a simple negation, which is trivial. The question is whether the negation must always be present.
Light is an actual physical thing, so you can discuss it purely in terms of physics. It is quantifiable. We normally discuss it in the context of typical human experience, which defines it in the context of darkness, but you could still discuss the physics of light with a blind person. "Good" and "bad" are purely conceptual; I don't think you can intelligibly discuss one without explicitly or implicitly discussing the other. Most ethics are therefore an attempt to establish a measurable quality that can be associated with the concept of good and, sometimes explicitly, sometimes implicitly, evil. Consequentialist ethics are probably the most overt at this, but really this is the fundamental premise of all ethics, and none of them have cracked it yet.
Following this thread is interesting to me in that it keeps circling back to fundamental disagreements about the definitions of moral actions, despite the OP's attempt to narrowly prescribe them. For me, and for any MMR adherent, that is an entirely predictable outcome, because attempts to objectively define an inherently subjective concept ultimately collapse into incoherence. That's why I think the optimal outcome is to just decide on what works best at each table and not worry too much about how others are doing it. It's also why, even though I don't bother worrying about "alignment," I also don't care that some of my players choose to use it (a Lawful Good paladin, for example). In fact, I think that the players and their characters having different ideas about alignment makes for better stories.
Edit: I also want to strongly emphasize that taking a MMR position does
not mean abdicating ethical responsibility or judgment. To the contrary! It means recognizing that we while we
need ethics, we must always be open to the possibility that our ethical judgment in a particular situation is wrong, so that we maintain flexibility and an awareness of the importance of context. And we recognize that ultimately most ethical decisions are pragmatic choices (meaning pragmatic in the philosophical sense).
There is a perpetual critique, especially from self-righteous quarters, that advocating for an MMR position is the same as advocating for moral anarchy, but that is the exact opposite of the MMR position. I consider myself a highly ethical person, while also recognizing that my ethics are contextual.