What’s the most effective way to debunk moral relativism / subjectivism?

[Cirion Spellbinder]

I’ve never been able to successfully explain this to someone except for my brother. I always try to be clear that I’m not referring to any universal will, just that if someone wants to be moral, there is a correct way to do it and a correct definition of morality. Mostly people just like to point out that moral perceptions have changed over time or suggest that ethical knowledge is distinctly manmade, unlike science and math (which are also manmade but somehow different apparently).

[carnap]

Just to note, "moral relativism/subjectivism" aren't the only positions that deny objective morals. There are a various of anti-realist positions you can have, for example, various forms of moral nihilism.

Without some sort of divine will, I really don't know how you would justify objective moral "truths".

[brimstoneSalad]

While there's not an easy answer to outright denial, most people aren't nihilists and aren't keen on adopting nihilism as a defense against realism, so it's usually a fairly easy sell when you demonstrate the problems with relativism/subjectivism.

I linked to this in the other thread, and it looks like you already started that new thread so I'll link it here too:
wiki/index.php/Objective-subjective_distinction

What you're describing sounds like cultural relativism.

Do those people you talk to believe that slavery was moral when it was considered moral? Do they believe that men beating their wives is moral in the societies that consider that moral?
If not, they have a problem.

Another huge problem for cultural relativism is the question of where to draw the line: it quickly decays into individual relativism/pure subjectivism.
Cultures break down into subcultures smaller and smaller, until you're dealing with an individual perspective.

Just asking enough question of their beliefs about morality should reveal them to be absurd. Most people seem to favor a realist/objective position over full on subjectivism that makes morality useless (might as well be nihilists) since for a subjectivist everybody is right in his or her own mind and moral statements aren't really meaningful beyond expressions of feeling/personal preference.

[Cirion Spellbinder]

Just to note, "moral relativism/subjectivism" aren't the only positions that deny objective morals. There are a various of anti-realist positions you can have, for example, various forms of moral nihilism.

I'm aware of the existence of those positions, but not that aware of the positions themselves. I'm currently doing some reading on metaethics, do you recommend any particular resources?

Without some sort of divine will, I really don't know how you would justify objective moral "truths".

Given the law of excluded middle, there must be only some moral truths as all of them being false or all of them being true, contradictions arise. I don't think there's a universal compulsion to act on them or any supernatural rewards.

[Cirion Spellbinder]

Do those people you talk to believe that slavery was moral when it was considered moral? Do they believe that men beating their wives is moral in the societies that consider that moral?
If not, they have a problem.

The last person I spoke to indicated to me that morals change over time like you've described.

Another huge problem for cultural relativism is the question of where to draw the line: it quickly decays into individual relativism/pure subjectivism.
Cultures break down into subcultures smaller and smaller, until you're dealing with an individual perspective.

What if they are willing to concede that?

Just asking enough question of their beliefs about morality should reveal them to be absurd. Most people seem to favor a realist/objective position over full on subjectivism that makes morality useless (might as well be nihilists) since for a subjectivist everybody is right in his or her own mind and moral statements aren't really meaningful beyond expressions of feeling/personal preference.

What if they are nihilists?

[Porphyry]

Just to note, "moral relativism/subjectivism" aren't the only positions that deny objective morals. There are a various of anti-realist positions you can have, for example, various forms of moral nihilism.

Without some sort of divine will, I really don't know how you would justify objective moral "truths".

Thanks for pointing this out. Without a source for moral standards, meaning a transcendental source, I do not see how there can be a foundation for objective morals. I've never seen a satisfactory answer to this.

Thanks again.

[Cirion Spellbinder]

Thanks for pointing this out. Without a source for moral standards, meaning a transcendental source, I do not see how there can be a foundation for objective morals. I've never seen a satisfactory answer to this.

What prevents the transcendental source from requiring a transcendental source?

[brimstoneSalad]

What if they are willing to concede that?

Then they are essentially nihilists, they can not criticize others on moral grounds, and moral discourse means nothing to them.

What if they are nihilists?

What's a math teacher do when a student comes in and says he or she doesn't believe in numbers and doesn't accept the legitimacy of mathematics?

A teacher might fail the student, or use that as a threat.
Not much you can do to compel them.

Thanks for pointing this out. Without a source for moral standards, meaning a transcendental source, I do not see how there can be a foundation for objective morals. I've never seen a satisfactory answer to this.

What do you mean by foundation?

Do you think the same applies to mathematical standards, or standards of logical discourse? Are you a presuppositionalist?

[Cirion Spellbinder]

What's a math teacher do when a student comes in and says he or she doesn't believe in numbers and doesn't accept the legitimacy of mathematics?

In case others were listening though, how do you explain that the axioms of mathematics are no less reasonable to assume than the axioms of ethics?

[brimstoneSalad]

What's a math teacher do when a student comes in and says he or she doesn't believe in numbers and doesn't accept the legitimacy of mathematics?

In case others were listening though, how do you explain that the axioms of mathematics are no less reasonable to assume than the axioms of ethics?

Usually teleology, that is: use/function.