There is an issue in the discussion of morality having to do with the meaning of moral terms. It came up in a recent comment where the author questioned whether the actions of an altruistic mouse or a cub-killing lion can be called "moral" or "immoral".
This attaches to the question of what moral terms mean.
Luke Meuhlhauser, with whom I have worked a few times, suggests a view called "moral pluralism". He holds that moral terms do not have one meaning - that they have different meanings for different people. With each different set of meanings there is a theory that corresponds to that set. Therefore, there isn't one moral theory that is correct. There are countless moral theories.
This sounds like moral relativism, but it is not. Objectively, these theories do not contradict each other - because the world itself does not contain contradictions. However, people speaking in one language may utter statements that appear as if they contradict the claims made in another theory.
For or example, one person may hold that what is right is that which is commanded by God, and what is right is that which is permitted by God is one moral theory. She uses "right" to literally mean "that which is commanded by God" and "wrong" as "that which God prohibits."
Another may use "right" to mean "that which maximizes utility", and "wrong" to mean "that which does not maximize utility is another theory".
These are two distinct moral theories. Both of them are legitimate. Both describe a way in which a person may choose to use moral terms. Both theories are correct.
However, these theories cannot contradict each other is because, no matter how we choose to use the terms, this will not change what is real. A person can have a theory that says that what is right is that which is commanded by God, but thinking it does not make it the case that there is a God that holds anything to be right.
Another person can have a theory that a right act is the act that maximizes utility. However, we can then ask, "What is literally true of the act that maximizes utility"? Does it follow that people generally have reason to praise such an act? Does it follow that the agent himself has a reason to perform that act? Does it follow that the act has a property of intrinsic goodness? Declaring an act "right" does not change its properties. Nor does it, by itself, give agents a reason to behave differently.
When somebody adopts a moral theory, they do not necessarily adopt a set of beliefs about the world. Adopting a moral theory is to adopt a language - to decide to use moral terms in a particular way. When two people adopt two different moral languages, they will sometimes have trouble communicating. Because those languages are very similar to each other, they may be confused about the nature of their disagreements - mistaking differences in languages as differences in beliefs.
On this account, desirism is one theory among many. I can defend the claim that desirism explains more of the use of moral language than any other theory. It makes sense out of the types of evidence that people usually bring in to defend moral claims. It is a theory in which some moral claims are true. However, it is still just one theory out of a very large set of possible theories. Meaning, it is one language out of a near infinite set of possible languages.
This view suggests that it might be better to abandon moral terms entirely. We should just be rid of them and, instead, simply stick to the propositions themselves and whether they are true or false.
Rather than saying that an act that maximizes utility is right, we can simply stick to the fact that it maximizes utility. Rather than saying that which God forbids is wrong we can simply stick to the claim that God forbids it - which is always false, because there is no God.
Applying this to the comment I referenced earlier, I argued that moral concepts do not apply to the case of a rat freeing a confined rat. Moral terms apply to behavior that we have the capacity to control through social institutions such as praise and condemnation. It makes no sense to say that a person is evil because he happens to have bad genes. It makes as little sense as calling a tornado evil for destroying a school.
However, if we apply Muehlhauser's approach we could have a different answer. Me and the commenter are speaking two different moral languages. On my language, praise and condemnation only apply to behavior that can be (and is being) molded through praise and condemnation.
In a different languages, those terms "moral" could mean, "Behavior we would praise if it were done by a creature with malleable desires." "Immoral" would mean "behavior we would condemn if it were done by a creature with malleable desires". On this account, it does make sense to say that the rat that releases another rat from confinement performed a moral action and the lion that kills the antelope performed an immoral action. However, this still does not imply that either action is praiseworthy or blameworthy - because they were not, in fact, the consequence of malleable desires we have reason to inhibit or promote.
Language is subjective. We cannot give an objective argument to the effect that one definition is correct and another is incorrect. We may, at our discretion, freely agree to alter the definition of our words. However, the ability to freely change the definition of words does not imply a freedom to alter reality. We can agree to use the term "carbon" to refer to atoms that have 8 protons rather than atoms that have 6. However, our decision will not alter the properties of atoms that have 8 protons or of atoms that have 6.
Muehlhauser presents a tempting view - and I have adopted it to some extent. In many cases, rather than fight about the meaning of moral terms, I simply provide the description and its implications and set the moral language aside. For example, instead of saying that something is wrong, I argue that people generally have many and strong reasons to condemn it, and then give those reasons. Functionally, this says everything that I mean to say when I say that something is wrong. So, then, why add all of the confusion and complexity of actually using the term "wrong"?
This implies a reduced interest in arguing that desirism is the best moral theory and, instead, simply using the propositions that make up desirism (without the morally laden terms) to make the same claims in a less confusing language. Why put a lot of effort into arguing that desirism is the best moral theory when, instead, you can argue that people generally have many and strong reasons to condemn violations of freedom of speech, or having sex with children - or to praise acts of charity or of pursuing education over mindless entertainment.
However, when it comes to entering into public debate on any subject, I do not think it is possible to leave moral terms behind. This, too, is likely to misinterpreted. Leaving moral terms behind may mean, to some, that everything is permissible (with each theory having its own account of what "permissible" means). This is not a legitimate implication. What is legitimate depends on how the term is used and if it makes a claim that is objectively true of that which is being called legitimate. Furthermore, I hold that people do substantially use moral terms in a way consistent with desirism. Therefore, desirism does allow one to communicate with people on matters of social importance in terms that they understand. Calling something wrong, for example, does, in fact, communicate that it is something that people generally have reason to condemn.
However, it is still a mistake to get caught up in a dispute of definitions that are not, at the same time, disputes over substance.