Here is an interesting exchange from the studio audience:
Writer 1: What is useful for us is what we want to do, not what tends to fulfill our desires.
Writer 2: I'm pretty sure that when I "want" something, that's the same as saying that it "fulfills my desires".
Writer 1: Then why do you care about a definition that is concerned with OTHER desires? It is simply not a topic of interest.
Let me answer that question:
First, of course, what we want and what fulfills our desires is exactly the same thing. What we want to do is a mere subset of what we want. And what is useful to us is often not what we want to do (exercise), but will help bring about something that we want (longer life with a greater ability to do more while living).
However, I don’t think these are side issues. The main issue can be answered as follows:
Do you really mean to suggest that I have no reason to be concerned with whether other people have an aversion to lying, stealing, rape, or murder? Their desires with respect to owning slaves are of no interest to me?
Now, let me add a bit more detail to that answer.
I would like to start with some remarks on egoism - the idea that the only (legitimate) interest a person can have is in himself or herself.
Egoists typically defend their view using a tight equivocation - a logical fallacy by which they are continually changing the definitions of their terms in order to dance around objections to their theory.
We can see this equivocal dance more clearly by introducing a couple of terms that more clearly distinguish between two different types of egoism: Subject-egoism and object-egoism.
Subject-egoism simply states that the beliefs and desires of the agent (the 'self' or 'ego') is the proximate cause of all of an agent's intentional actions. My intentional actions can be linked to my beliefs and desires. If an act cannot be linked to my beliefs and desires, then it is not my action.
Let's assume that some mad scientist invents a machine that allows him to take control of my body. He does so, then uses my body to rob banks and convenience stores and drop off the money where he can pick it up. Because those actions did not come from my beliefs and my desires, they are not my action - they are the actions of the person who took over my body. He is responsible for robbing those places, not me.
Subject-egoism is almost certainly true. Desirism includes the fact of subject-egoism when it states that the each person acts so as to fulfill the most and strongest of his desires, given his beliefs - and seeks to act so as to fulfill the most and strongest of his desires.
Object-egoism is the view that the self or the ego is the only object of one's desires. It states that the only thing an agent wants or desires is his or her own benefit. Other people, other things, things that are not of the agent himself are of no concern to him or her.
Object-egoism is almost as clearly false as subject-egoism is true. People, in fact, can have a number of other-oriented desires. He can have a desire that no child go to bed hungry, an aversion to the suffering of animals, or an interest in having the human race or its bio-mechanical descendants persist billions of years into the future. A person can have such a strong interest in the welfare of his children that he will run into a burning building to try to save them, or such an interest in promoting God that he will blow himself up in order to attack God's enemies.
The Egoist Dance
What the egoist does is he begins with object-egoism - asserting that the self is the only legitimate object of one's concern and one either cannot or should not have concern for any person other than the self. When he is challenged, he retreats into the unassailable position of subject-egoism asserting that the self is the subject of all of one's intentional actions. When the egoist's opponent quits attacking the unassailable position of subject-egoism and goes away the egoist steps out of subject-egoism and brags about how he has now defended object-egoism and forced the attacker into submission.
The proximate cause of all of an agent's actions are his own beliefs and desires. However, the self is not the only possible or the only permissible object of one's desires. One can well be interested in the well-being of others, and others have many and strong reason to cultivate those types of concerns in their neighbors.
A person can be made to hate lying. He can be made to hate lying in the same sense that he can be made to hate spinach or to hate spinach.
An agent's hatred of spinach does not spring from the belief that spinach is not useful-to-self. In fact, the opposite is true. Spinach is very useful-to-self. It provides the self with a number of benefits - far more benefits than chocolate cake, for example. However, some people cannot stand the taste of spinach and they refuse to eat it in spite of its benefits. They just don't like it.
An agent can be given the same type of hatred of lying. This hatred of lying does not spring from any argument that lying is always harmful to the agent. In fact, lies can often provide the agent with a number of benefits. However, people can be made so that they cannot stand the taste of lying and they refuse to lie in spite of the benefits that they would otherwise get from lying.
If I can cause other people to have a sufficiently strong aversion to lying, then I can trust that they will tell me the truth even under conditions when they would otherwise have benefitted from a lie. They would forego the benefits of a lie just as they forego the benefits of spinach.
I have many and strong reasons to build in others this aversion to lying. I also have many and strong reason to build in them aversions to theft, assault, rape, and murder. In doing so, I make them so that they will not commit theft, assault, rape, and murder even when they would otherwise benefit.
They have reason to build in me these same aversions. To the degree that they have done so, then they have made me so that I will not steal, assault, rape, or murder them when I might otherwise benefit.
This is all incorporated under the desire utilitarian slogan of promoting in others those desires that tend to fulfill other desires and inhibiting in others those desires that tend to thwart other desires. It is something I can do using the social tools of praise and condemnation, among others.
In doing this, I am making others so that they are less likely to thwart other desires in the subject-egoist sense, not the object-egoist sense. My motivation for promoting in others desires that tend to fulfill other desires and inhibit desires that tend to thwart other desires includes my interest in having humanity or its bio-mechanical descendents survive indefinitely into the future, and my interest that no child go to bed hungry.
My motivation to promote in others desires that tend to fulfill other desires includes the aversions to lying, theft, assault, rape, and murder that others have had reason to cause me to have.
When I get together with others, it also makes very good sense for us to talk about which desires we have reason to promote using social forces of condemnation and punishment, and which we have reason to inhibit. It makes perfectly good sense for us, using language, to invent a word to refer to desires that people generally have the most and strongest reasons to promote or inhibit.
Yes, I am acting on my subject-egoist desires. The desires that actually motivate my actions are my own. How can they be anyone else’s and still be my actions? However, it would be absolutely foolish of me to have no interest in what desires other people have. Of course I have an interest in other desires – as does every rational agent – because the desires that other people have will help to determine whether my attempts to fulfill my desires are fulfilled or thwarted.