Any Moral Relativists in the House?

[HappySkeptic]

I did manage to dig up an article by Boghossian where he argues my thesis. The thesis is: realism and nihilism are tenable positions (ie coherent positions that take a clear stance on the status of moral facts) while relativism is not. Why? Because relativism simply lists what is permitted according to the values of culture x, y, or z. And thus gives only a factual account of these cultures' beliefs. But the debate about moral realism's status isn't a debate about what a given culture believes. It is a debate about normative claims.

If there are absolute moral truths, then one of two things must also be true

1) There is a reason for that truth that cannot be determined by humans (i.e. God-given and God-understood only)
or
2) There is a reason for that truth that can be determined.

If 1) is true, then we simply have to accept the moral truths given by gods.  If 2) is true, then we must be able to reason why the moral truth is "true".  It must either be a scientific statement that can be tested, or it must follow from some higher-level values.

I have yet to find many statements of morality that can be scientifically or logically tested beyond Sam Harris' "maximal unhappiness is bad" - and that even assumes that unhappiness is bad (a value statement, linked to biology).

Moral "truths" must be inferred from human nature, and societal interaction.  Human-nature comes with a wide variance, so that can only rarely used as some sort of objective argument for moral truth.  Cultural interaction has some similarities among cultures, but also has a wide variance.  Again, culture cannot provide objective moral truth.

Unless we defer to gods, the only things we have for judging morality is values.  Sometimes we can agree on values, owing to our common nature.  Sometimes we can't.  Either way "common agreement" is not the same as objective morality.