If I'm right that moral language refers to a conventional but incoherent set of goals, why bother with it? Instead of arguing about whether a war is wrong or right, we could talk about how the war promotes or opposes specific goals, e.g: "This war greatly increases human suffering" or "This war addresses deep inequality." Discarding moral language would clear up much confusion.
A Federation of Goals
Then again, clear communication might not be the main point of using moral language. Suppose I only care about reducing suffering, not inequality. Maybe I buy slaves and treat them well enough that they're happier as my slaves than they would be on their own. Meanwhile, you care about equality issues beyond any consideration about suffering. If you point out that keeping slaves is bad for human equality, my response would be: "So what?"
Now, suppose you start talking about both suffering and inequality in unified terms. You also use shared terms to praise people who relieve suffering or inequality. Through the power of association, you may start to influence my view of slavery. This is especially effective if lots of people use the unified terminology to associate the goal I didn't care about with the goal I did care about.
I'm suggesting moral language gets its punch from artificially combining the psychological importance of several goals under one way of speaking. Think of it as a union or federation of goals.
There's a persistent worry that understanding the nature of ethics will undermine the practice of ethics. While the view I'm expressing here does challenge the existence of any uniquely moral facts, I think it's the goals behind morality we're really committed to in the first place.
"Genocide is wrong" isn't some brute fact; we call genocide wrong because it entails so much harm and injustice...and these facts don't change if we take away the word "wrong."
When people say "Good folks donate to the needy" what are they doing?
Usually either prescribing charity directly or promoting an implied goal and recommending charity as a way to advance that goal. The Expressivists and Prescriptivists are largely right about what's going on in the "doing" part of moral discourse. I just think truth claims play a role too. For example, since moral goals are fairly conventional, a disinterested person (e.g. an observant psychopath) could be stating the fact that charity advances conventional moral goals.
How This Helps
I hope this view can shed light on what's really going on in moral disputes. If we can sort out which goals are at stake when one person says "good!" and the other says "bad!", it may turn out they're debating facts relative to the same goal (e.g. whether a social program really is better for a particular goal) or expressing a commitment to different goals (e.g. the social program is better for a short-term goal but not for a long-term goal). Either way, the debate can be put in new and hopefully more fruitful terms.
In future posts, I plan to analyze specific moral disputes from this perspective. I'll also be looking at how goal-relative moral naturalism might handle problems in the philosophical literature.