I have noticed that there are people who draw support for some type of individual subjectivism (moral claims are mere expressions of personal preference) from the fact at a person does not make a moral claim unless he wants his audience to accept that claim.
There are, of course, exceptions such as satire or acting. However, sincerely stated moral propositions always express a desire on the part of the speaker that the audience adopt that prescription. This is thought to support the thesis that moral claims are nothing more than expressions of personal preferences – expressions of the desire that people adopt a particular attitude.
The mistake here comes from the fact that speech acts are generally intentional actions. Exceptions exist, but we are not concerned with the exceptions in this context.
As an intentional action, an speech act always expresses the desires of the speaker. The speaker will always choose what to say based o what will fulfill the most and the strongest of the agnt’s desires, given his beliefs. In other words it is true that, in the vast majority of cases, a person will not say, “X is wrong” unless he has a reason to act so as to realize a state of affairs in which X does not occur.
However, the leap from here to the conclusion that moral claims are nothing more than statements of individual preferences is entirely invalid.
All intentional claims are speech acts. Every one of them.
If I were to say, “There are over 600 known asteroids that are closer to the moon in terms of delta-v (or in terms of the amount of fuel needed to get there and back again,” this is an intentional statement. I wrote it on purpose.
This intentional act, like all intentional acts, can be explained in terms of the beliefs and desires of the agent. I wrote it because I had a desire to make a particular point and a belief that the use of this example would illustrate that point. Also, we can explain this intentional act in part in terms of my interest in space development, urging me to use that example instead of any of countless other alternatives.
Yet, this does not imply that the proposition about the 600 asteroids is merely an expression of my desires. That is to say, the reasons that I may have for uttering such a proposition are grounded on my desires, but the truth value of the proposition that I have uttered is independent of my beliefs or desires.
The same can be said of moral claims. The fact that a person is not motivated to make a particular moral claim unless doing so fulfills the most and strongest of my desires (given my beliefs) to utter it does not prove that the truth value of the statement is linked necessarily to his desires.
It is still quite possible that he was motivated to make a statement about intrinsic value, or God’s wishes, or widespread evolved disposition, or whether many and strong reasons exist to inhibit a particular desire. These are legitimate subjects for an agent to talk about when it fulfills the most and strongest of his beliefs given his desires to talk about them.