In my last posting, I presented two propositions:
(1) The only sensible answer to a "should" question (e.g., Why should I do X?) is to present the agent with some reason for action that exists, or some fact that ties the action or its consequence with some reason for action that exists.
(2) Desires are the only reasons for action that exist.
This means that the only sensible and true response to a "should" question is one that relates that action or a consequence of that action to one or more desires.
I presented these against the idea that desirism has some hidden moral commands. These claims tell us something about "should" statements, but they are not, themselves, "should" statements. They tell us, in effect, what facts in the world to look at to provide true and relevant "should" statements.
Now, I want to add the proposition:
(3) Desires only directly motivate the people who have them.
This relates to another objection that I often hear - that desirism claims that each person has some sort of special motivating reason to consider the desires of all other people. The argument is that no such special motivating reason exists, so desirism is to be rejected.
So, actually, the important corrolary to this claim that I actually want to focus on is that desires do not directly motivate - or provide any direct reason for action - to those who do not have them. In order for Agent A's desire to motivate Agent B, then the fact of Agent A's desire must be seen as relating some how to a desire that Agent B has. This could be a desire to fulfill Agent A's desires, or a desire to negotiate with Agent A for mutual benefit, perhaps.
I may ask, "Why shouldn't I talk out loud at the movie theater?"
The answer may be that it disturbs the other customers.
That it disturbed the other customers is a true statement. It is also true that the answer relates the act in question - talking out loud in the movie theater to reasons for action that exist. It this case, it relates the action to the desires of other movie-goers. So, it is a true and legitimate answer to the question.
However, this answer may not provide the talker with any motivation to quit talking.
The talker could simply not care that the other customers are disturbed. He may actually want to disturb the other customers - in which case telling him that talking during the movie disturbs the other customers will give him all the more motivation to talk during the movie.
This is all part of desirism.
There are two facts to note that correspond to this claim.
The reason that only my desires can motivate my action is because only my brain is hooked up to my body in the right way. My actions come from my brain and nowhere else.
The other, far more important fact to consider is that if somebody else's desires were in control of the movements of this body, then they would not even be my actions. If somebody were to hook up a device where they controlled my movements, then the actions of this body would be his, not mine. To say that the actions are mine says that they come from my brain, or my mind.
The objection that desirism asserts that each agent has a special motivating reason to consider the desires of others is false. Desirism denies the existence of any such reason. Furthermore, this denial actually plays an important role in the moral theory.
If agents really did have a direct motivation to consider the desires of others, then morality would not be necessary. The mere fact that actions fulfill or thwart the desires of others would directly motivate the actions of each of us, and give us no need for morality.
However, there is no such special motivation. Desires only provide motivating reasons for the agents who have them. The desires of other agents can be used to offer true and relevant answers to 'should' questions, but will only motivate the agent one is talking to according to how this fact of the desires of others fits with the desires of that agent.
The objection that desirism denies this fact - is a misplaced objection.
Let me say it gain to be clear.
Desires only directly motivate the people who have them.