Desire is an attitude aimed at the good in which we believe that we can have but that we doubt that we will have or doubt that we will continue to have. We cannot desire what we securely have and know that we will not lose. But it is also true that insecurity is one of the problems that prevents us from being happy. So is it possible for a perfectly happy person to desire something? A perfectly happy person is one whose willing and desiring are the same act.
A perfectly happy person is someone who is completely satisfied with his condition and whose condition is such that he will continue to be satisfied into the future. There is an objective element and a subjective element. The objective element is the truth of whether or not he will actually continue to be satisfied into the future. The subjective element is whether or not he is satisfied right now.
If he is satisfied right now, then he will not lack anything good right now. The sort of lacking that he cannot have is the kind that he would desire. Therefore, it is impossible that he desire anything that he lacks right now. If he did, then he would not be perfectly happy. Neither will he believe that he will lack anything in the future. So he will be unable to desire anything in the future either. So it appears that a perfectly happy person will be unable to desire at all.
But there is an alternative way of defining desire. Any rational action is an act of the will. This act of the will takes what the person believes to be good and wills it to happen. The reason why this action is chosen in particular is because the person desires it. But desire is simply viewing it as good. So we could also claim that the person believes that it is good because he knows that he will will it to be. His willing of the action and viewing it as good are identical. This kind of desire is still possible in a state of perfect happiness.
It is not possible to desire in a state of perfect happiness if the desire is understood to be distinct from the activity. If the desire is understood to be the same as the activity, then the desire is possible. Desire is either an attitude aimed at the good which we lack or believe we will lack or it is the willing of a something good. The first kind of desire is both the willing of something good and the lack of something in the present. The second kind of desire is simply the willing of something good. This means that the first kind of desire – the one that we are most familiar with – includes elements that are not essential to desire as such.
This is not the end of the matter though. There is also the issue of whether or not perfect happiness is compatible with willing what is instrumentally good. There is also the issue of whether or not perfect happiness requires moral perfection.