When I consult my intuition, it seems evident that the "truth" or "falsity" of moral statements plays an important role in securing their normative force. For instance, take the statement "it is wrong to kill." It would stand to reason that a statement of this sort is morally binding, if and only if it is "true" that the act of killing is wrong. To give some traction to this view, I call a statement "true" if it is either (1) non-contradictory (i.e., analytic) or if it (2) expresses a proposition about some state-of-affairs that obtains in the world (i.e., descriptive). Since moral statements usually pertain to the assessment of acts, I will assume (2) is a more relevant criterion for assessing the supposed "truth" or "falsity" of moral statements.

According to (2), the statement that an act "x" was voluntary or intentional on the part of an Agent "A" is to make a causal statement that "x" was initiated by some act of "A's" mind that was an act of bare will -- a volition or an act of A's setting himself to do x, or an act of intending to do x, or the like. On the basis of (2), a causal statement of this sort expresses a proposition that can be checked against the world, and can therefore be assessed for truth-value. It is either 'true' that A intended to do x, or 'false' that A intended to do x.

But my question is: Is it really the case that moral statements describe causal states and therefore express propositions? If they do not, then moral statements cannot be regarded as "true" or "false." If this is the case, their normative force seems to evaporate. Hence the problem.

It is my view that moral statements do not express propositions and are (therefore) neither "true" nor "false." Take voluntariness or intentionality. To say an action "x" was voluntary on the part of agent "A" is NOT to describe the causal process whereby 'A' brings 'x' about. It is to ascribe 'x' to 'A'; that is, to hold 'A' responsible for it. Now, holding a man responsible is a moral or quasi-moral attitude; and so there is no question here of truth or falsehood, any more than there is for moral judgments. If "B" agrees or disagrees with "C's" ascription of an act to "A", "B" is him/herself taking up a quasi-moral attitude toward "A." Now, here's the ethical import: While facts may support or go against such a quasi-moral attitude (perhaps "A" never did "x" in the first place), they can never force us to adopt it. Hence, the normative weight of our moral statements seems to disappear.

Any thoughts? Can moral statements be true? Does the truth of moral statements determine their normative weight?

It seems to me that you are trying to use the ambiguity of the free will question to also call into doubt moral responsibility, and as we have seen elsewhere, that's not the case at all. Just because progress seems to be lacking on the free will issue does not mean that morality goes out the window too.

If A decides and carries out x (murder, for example), then it is both true that murder is wrong and A is guilty of it. Juries make these kinds of assessments every day.

Why shouldn't a moral statement describe causal states? Suppose we want to express an ethical assertion like this:

"Murder is wrong."

Further, suppose we know that Alice murdered Bob. And suppose we have another proposition

"Those who do wrong are guilty."

Then we have

"Alice committed murder." => "Alice is guilty."