Some members of the studio audience have focused attention on my use of the term 'generally' when I talk about a desire being good or bad. The claim is that this term is too vague, and they wish to have something that is more precise.
This objection has been raised specifically against my use of the term in discussing evil:
A person is evil to the degree that he has malleable desires that people generally have reason to inhibit (because that desire tends to thwart other desires), or to the degree that he lacks a malleable desire that people generally have reason to promote (because that desire tends to fulfill other desires).
However, it applies more generally to any part of the theory in which I use the term 'generally'
As one member of the studio audience put it:
Perhaps my biggest issue, when it comes to accepting DU explanations and definitions, concerns the term 'generally'.
When I use the term 'generally', I am using the term in the same way that a person might say that the prevailing winds in the United States generally come out of the west, or that the bus generally shows up on time. It means that you might be able to find me one or two exceptions – instances in which the wind is not blowing from the east or in which the bus was late. However, these findings will not defeat the proposition that a particular desire generally tends to fulfill other desires.
In other words, do not come to me with a wild story in which, quite by chance, an act of rape happens to provide all sorts of benefits. This will not defeat the thesis that a desire to commit rape is generally a desire that tends to thwart other desires.
Or do not come to me with a story about how a robbery victim was shot in the head and the damage happened to cure his obsessive compulsive disorder. This does not challenge the claim that a shot to the head can generally be understood to thwart most of the desires of the person who has been shot.
We have reasons for action that exist to promote an aversion to committing rape and an aversion to shooting people in the head based on the fact that rape and shooting people in the head generally can be expected to thwart desires, not fulfill them.
One of the most common forms of objection to act-utilitarian theory is to invent some exotic story in which an action that can generally be expected to produce negative utility happens in this one instance to maximize utility. The doctor has a chance to kill a healthy patient to save five patients who would otherwise die, or reporter is told that if he executes a single villager then the evil warlord will spare the lives of 20 villagers and the warlord can actually be trusted.
Desire utilitarianism is not open to these types of objections because it is not concerned with the rare and exotic story in which utility is promoted or inhibited. It is concerned with whether a desire generally fulfills other desires, not with whether it fulfills other desires in every single instance.
Furthermore, there is a reason to be concerned with whether a desire generally fulfills or thwarts other desires, rather than whether it fulfills or thwarts other desires in every instance. This is not just an arbitrary condition tacked on because it allows me to avoid objections like those raised against act-utilitarianism.
It is justified by the fact that desires are persistent entities. They do not come and go on a whim, and people cannot turn them on and off at will. A desire, once cultivated, will be there to motivate a range of different actions over an extended period of time. It does not make sense to be concerned with whether a desire fulfills other desires at every single moment during its long life. What matters is that, over its long life, it tends to generally fulfill other desires.
So, this is not some ad hoc qualification tacked on for no reason other than that it allows me to side-step a family of objections. It is a qualification required because of a certain set of facts about the world – that desires are persistent entities that are capable of generally fulfilling (or thwarting) other desires even though one can imagine strange and exotic cases in which they thwart (or fulfill) desires.