In one sense, this is an easy question: Desirism is the moral system of Alonzo Fyfe as promoted on his blog1 and in his collaborative podcast with Luke Muehlhauser.2 At the same time, it's a hard question because Fyfe's views have changed significantly over time and no definitive sketch has been kept current. My purpose here is to sketch what I think Desirism is all about, and update this post when my own understanding of his moral system changes.
The following sketch will be in my own words, since I'm interested in the ideas, not Fyfe's phrasing or style of explanation. Nor should anyone take this as anything more than a bystander's attempt at describing Desirism. I am not speaking for or against the system here.
Current version: 1.3.2 — last updated May 10, 2011
Proponents of moral systems tend to start with some aspect of morality which they have an insight about, then they try to account for other aspects by building on this core. Desirism's starting point is an explanation of human behavior, or as philosophers would say: an action theory.3
Action theory is relevant to moral theory, since the question of how voluntary action works can bear on the question of which actions, morally speaking, we ought to perform.
I won't get into all the details of Desirism's action theory, but basically: a person's attempted actions are determined by their desires and beliefs. If I want a cookie and I believe a cookie is in the left jar instead of the right jar, I will try to open the left jar...unless I have some stronger desire which outweighs my cookie desire.
This might sound a tad obvious and silly, but it is a substantial claim. It's opposed to the notion that we can act 'from duty' against all our desires, which is how Kant defined moral action.4
It follows from the above that if we want someone to make a different choice in a given circumstance, we must either change her desires or her beliefs.
From what I know of Fyfe, he doesn't advocate making stuff up to shape the beliefs of those who buy into it. Instead, he focuses on the process of social praise and condemnation to shape the desires of those affected by such peer pressure.
Suppose most people in a population don't like rock music. Heck, they don't even like thinking about other people listening to rock music. What's going to happen? Some of them are going to condemn rock music and, probably, some others who like rock music will start to like it a little less. (This may backfire with teenagers.)
I see a parallel here with biological evolution as a way of describing the "change in the frequency of alleles within a gene pool from one generation to the next."5 Desirism can be seen as a model for the dynamics of held-desires in a population over time.
What does it mean to say an action is 'morally wrong' or 'morally right'? This is where Desirism gets fuzzy, in part because the detailed podcast series hasn't gotten around to addressing this yet. Here's how Fyfe seems to handle normativity:
When we say a person 'ought' to do X or 'ought not' to do Y, we are implying there is a reason for taking (or not taking) an action. According to Desirism, desires are the only possible reasons for taking an action. (At least when mistaken belief isn't complicating things.) And therefore, strictly speaking, 'Sam ought to do X' is only true if X properly corresponds to Sam's desires.
Wait, what?! Doesn't this throw moral right and wrong out the window entirely if Sam only 'ought' to do whatever conforms to her personal desires?
Not so fast. Desirism locates normativity at a different level than usual. Instead of focusing on what agents ought to do in a given situation, Desirism focuses on which desires agents ought to have. The colloquial assertion 'Sam ought to do X' is taken as an elliptical form of, 'Anyone ought to have Z desire[s], which would lead Sam to do X.'
What are these desires 'anyone ought to have' and how can we justifiably claim people 'ought' to have them? We can answer both at once: the desires 'anyone ought to have' are those which — when held by individuals — fulfill other desires more so than thwart other desires. Just as the desires an individual happens to hold justifies her taking desires-fulfilling action, the full set of desires held by desiring beings justifies their holding desires-fulfilling desires.
Of course there is one big difference between these kinds of 'ought.' An individual will invariably do what she 'ought' according to her own desires. That's just how people work. But an individual might not hold the desires she 'ought' to hold according to desires considered more generally. Furthermore, she's not going to be intrinsically motivated to hold these — as Fyfe calls them — good desires. She must be extrinsically motivated, and this happens through a process of peer pressure, as explained in the Shaping Behavior section above.
When we say a person did 'wrong,' we're applying social pressure against anyone listening to not desire doing the condemned thing. Vice-versa for calling an action 'right.' According to Desirim, there is an important sense in which such judgments can serve more than just an emotive role: they can be correct or incorrect insofar as the desires being encouraged (or discouraged) facilitate other desires.