People say your committing murder is intolerably wrong and that is a mere fact. They add that it would not matter if a demon would imprison persons forever if you refused to commit it.
This seems to say objective morality is not just true but truth itself. It is like violating it attacks all truth tacitly even if the agent does not see it that way. That is why it is so serious.
The thought experiment touches on a core principle in metaethics: moral realism. It argues that moral truths exist as fundamental facts of reality, independent of human opinion or consequences. The scenario described tests this by asking if an action is wrong even when there are immense negative consequences for the individual (the demon's prison).
The scenario highlights the idea that the wrongness of murder isn't just an opinion, a feeling, or a social construct. If it were, the threat of eternal imprisonment might outweigh the moral rule. Because the act remains fundamentally wrong despite extreme coercion, the moral fact is treated as an objective truth.
Philosophers like David Hume noted that you cannot derive an "ought" (a fixed moral rule) from an "is" (a physical observation). This thought experiment suggests that moral truths are an entirely different, irreducible category of truth, fundamentally existing regardless of what the universe or any entity commands.
Universal Realism vs. Relativism: This view directly opposes moral subjectivism. If moral truths are simply true in the truest sense of the word, they apply across all times and universes, regardless of whether a culture, a human, or a demon accepts them.
COMMENT: How can rewards be rewards or joy be joy if virtue and morality
are such a threat? If they say the rule matters not the suffering? In
fact having a fun life would tempt you to kill the person to spare your
friends the horrors of an eternal prison. It would amount to
self-temptation. The argument gives a morality all right but not a human
one.