The issue of favoritism deals with a feature of morality whereby people seem, at times, to have a moral permission (or even an obligation) to favor their own friends and family while, at the same time, are under an obligation to regard the interests of everybody equally.
To illustrate the issue of favoritism, one simply needs to consider the last gift that one either gave or received. The chances are very slight to the point of non-existence that the gift was given by somebody who weighed all interests equally and gave the item most needed to the person who needed it. Instead, that gift was bought for a a family member, a friend, or a co-worker who, at the time, was not the person on the planet most in need of a gift..
Desirism deals with this tension by using a two-tiered system of evaluation. At one tier actions are evaluated by whether they are actions that a person with good desires would perform. At this level, it is possible to argue that a person with good desires is somebody who has special affections for members of their own family and their own friends. These sentiments would motivate the agent to give special weight to their interests and concerns.
However, this evaluation of desires takes place as a second level where all agents have equal weight. The level at which we determine that there are good reasons to allow individuals to have special affections for those who are near to them we give equal weight to the interests of all people.
The most widely accepted interpretation of John Stuart Mill's Utilitarianism is that it represents a two-tiered moral theory known as rule-utilitarianism. Actions are evaluated according to whether they are consistent with the best rules. Rules, in turn, are evaluated according to whether they maximize utility. As agents engaged in day-to-day activities, we do not have the time or the resources or even enough data to determine the utility of each individual action. In order to decide what to do, it is more efficient to invent a set of rules where actions consistent with the rules will tend to maximize utility, and to judge actions by those rules.
When faced with the question of whether to lie to a grand jury, one applies the rule, "Do not lie to grand juries." When deciding whether to have a rule against lying to grand juries, one looks at the overall utility of having such a rule.
Richard M. Hare also used a two-tiered moral system. According to Hare, moral claims are commands of the form, "Do this." and "Do not do that." These commands are given to people in their role as "proles" or mere followers of orders. However, there is a second level of moral thinking that Hare calls the level if the arch-angel. At this level, we examine the commands to determine which commands produce the most utility.
When faced with the question of whether to lie to a grand jury, one yields to the command, "Do not lie to grand juries." When deciding whether the arch-angels would command us not to lie to grand juries, we ask whether the arch-angel would see that such a rule maximizes utility.
Both of these two-tiered systems make it possible to justify acts that favor one's own friends and family or the people nearest an agent.
We can understand this argument by examining a relevantly similar decision that might be made by the CEO of a massive multi-nation company. The company is far too big for any person to manage efficiently. Therefore, the CEO decides to divide the company into regions and to assign a vice-president to each region. Even though the CEO's concern is with maximizing profits (maximizing utility), this end is best achieved by giving each vice-president the following instructions:
Do not concern yourself with overall profitability. That is my job. You are explicitly prohibited from looking at each region with indifference towards any other region. Insead, you are commanded - or given a rule - to concern yourselves with what is going on in your region. Focus your attentions and concerns there. If you think that it is fitting to hand out performance bonuses to your employees, feel free to do so. Do not concern yourself with whether the employees in some other region could benefit more from such a bonus - they are the responsibility of some other manager who knows that region better than you. They are not your responsibility. You focus on your region.
The vice-president may, in turn, give the same instructions to the regional manager, and the regional manager may give the same instructions to each store manager. In each case, the individual is given a command or a rule not to be indifferent towards all employees in all departments in the company, but to look after those employees who are in a close relationship to himself or herself. They can even be expected to be evaluated as managers according to their success in taking care of their own region, store, or department.
By comparison, in society as a whole, at the level of the arch-angel or the rule-maker, we may instruct each person, "Do not weigh the interests of all individuals equally. Your job is to take care of your friends and your family. Let others worry about their friends and their family. In the same way that a department manager may decide on a departmental celebration or dinner, you are free to decide to provide gifts to your friends and family. You may feel free to buy a birthday gift for your own child and to seek their health and safety without being commanded to be indifferent to the interests of all children."
Of course, as with store managers and department managers, there are limits to what one may do in expressing their concern for the people in one's store or department - or for one's friends and family. Yet, these limits do not invalidate the call to have a special concern for people in the given relationship.
All the while, the rule or the command is justified at a higher level that weighs all interests equally. The CEO who makes the rule or issues the command still does so with an eye on maximizing the profitability of the company. Whereas society makes the rule or issues the command to individuals to take care of their friends and family with an eye towards maximizing overall utility.
Desirism also uses a two-tiered moral system. It evaluates actions according to what a person with good desires would do, and evaluates desires according to their tendency to fulfill other desires. At the level of evaluating desires, the interests of all agents are treated as equal. There is no call to give extra weight to the interests of some agents and to disregard the interests of others. However, at this level we can justify letting an each and every agent have special affections for their own friends and family. Consequently, a person who does what a person with good desires would do is a person who gives special attention to the interests of his or her own friends and family.
The difference between desirism and the other two alternatives is that desirism focuses on desires or affections rather than rules or commands. Rather than putting agents under a rule that allows (commands) them to give special consideration to friends and family, desirism says that the good person will have genuine affection for their friends and family. The parent who buys a gift for a child does not do so because an impartial rule tells him to, or an arch-angel commands him to. He buys the gift for his child because he has a genuine affection for and interest in that child.
At the level at which we ask whether people generally have reason to promote or inhibit these types of affections we treat all desires equally. Where we determine that there are reasons to allow - and even to promote - these types of affections, we allow that individual agents can act, and may well be encouraged to act, out of a special affection for their friends and family.