A member of the studio audience wrote:
[I]n support of the role of prescriptivity in moral language one might point out that the facts you're pidgeonholing as "moral" look like they fall more naturally under "enlightened self-interest" or somesuch.
"Enlightened self-interest" is an ambiguous term - having two possible meanings.
One of these meanings makes claims about enlightened self-interest trivially true - true in a very uninteresting and unimportant way. The other makes claims of enlightened self-interest false, though not so trivially false.
The distinction here is between interests OF the self versus interests IN the self.
Those who suggest that claims about enlightened self-interest are both true and important usually equivocate between these two meanings. They start off with speaking as if all interests we have are interests IN the self. They all aim for the benefit of the agent. When they are backed into a corner by arguments that show this to be false they switch the second meaning of self-interest - interests OF the self. This version of the theory is true, but does not have any of the implications of the version they began with. When their opponent gives up attacking this second (trivially true) claim, the advocate of self-interest theory declares victory and switches back to the first (false) definition of self-interest.
The trivially true version of self-interest (interests OF the self) states that an agent's actions are motivated entirely by the agent’s own desires. The desires of others may affect his actions - but only insofar as he has a desire to fulfill (or to thwart) the other person's desires.
This is true in a biological sense - only my brain is hooked up to my muscles in the right way. My choices have to come from my brain - meaning my brain states (my beliefs and my desires). They do not come from outside my brain.
More importantly, though, this is logically true. Let us say that you were to hook up a remote control device such that you could control my body remotely. Now it is your beliefs and your desires that control this body. If that is the case, then the actions that this body now performs are no longer my actions. They would be your actions. Actions belong to (are the responsibility of) the brain whose brain states (beliefs and desires) are the proximate cause of the choices controlling those actions.
That is to say, all interests that motivate an agent's action are interests of the self - the agent's own beliefs and desires. If they do not come from an agent's beliefs and desires, then they are not his actions.
When people talk about enlightened self-interest they tend to want to be saying something more robust than saying, "The desires that cause my intentional actions are the desires in my brain."
Now, the claim that all actions are motivated by desires OF the self is quite different from the claim that all actions are motivated by desires IN the self.
A desire IN the self is a desire that P where the self ("I") is the object of the desire - "I desire that I...". I desire that I experience pleasure. I desire that I have more money. I desire that I am admired by all.
While the claim that the desires that motivate an agent's action are desires OF the self is trivially true, the claim that the desires that motivate an agent's actions are desires IN the self is sometimes false. The range of possible desires that an agent can have is as broad as the range of possible beliefs that an agent can have.
An agent can have a desire that no child suffers, or a desire that a particular piece of wilderness remain untouched by humans. He can desire that humans (or their descendents) exist far into the indefinite future and desire that the SOB that kidnapped and raped that child be made to suffer for his crimes. Just as he can believe that a God exists, he can desire that a God exist. And just as he can believe that the claims made in the Bible are true, he can desire that the claims made in the Bible are true.
The desires that Jim might have that would give him reason to condemn bank robbers almost certainly includes some self-interested desires (he desires that his money be safe), but it could also include desires in things other than the self. he may desires the well-being of others for its own sake - not for any benefit it may provide to him. He sees a society where bank robbing is rampant as one of widespread suffering and condemns bank-robbery as a way of reducing that potential for suffering.
Desirism says that Jim's reasons for actions that exist for condemning bank robbers must necessarily be his desires - desires OF Jim. But it not necessarily be desires IN the self - desires of which Jim is the object.
Perhaps more importantly, the desires that agents have reason to create in others are often not desires IN the self. In fact, praise and condemnation are more reasonably used to inhibit or reduce desires in the self (selfishness) and to promote desires OF the self that are desires IN the well-being of others, or desires in things that tend to lead to the well-being of others, or aversions to things that tend to thwart the desires of others.