Some years ago, Judge Posner wrote that "[s]elf-control is not only an emotion but a strong emotion because it is a check on strong emotions." (At page 324 of "Emotion versus Emotionalism in Law," a chapter in The Passions of Law (Susan A. Bandes ed. 1999). He seemed to say that "self-control" is needed in order to achieve "detachment."
Detachment is not a vantage point from which the judge is unemotional -- Posner believes "emotion is necessary to precipitate any decision that is not merely the conclusion of syllogistic or other purely formal reasonsing--the kind of reasoning a computer can do better than a human being. Decision is a form of action, and ... there is no action without emotion." (311) Rather, the detached judge is sufficiently distanced from the power of the emotional details of the situation immediately before him or her to be able to care also for those elsewhere, that is, for the long-term consequences of his or her decision. (Posner goes so far as to say that "contrary to the claims of its detractors, the economic approach to law is profoundly empathetic because, although it does not wear its heart on its sleeve, it brings into the decisional process the remote but cumulatively substantial interests of persons not before the court -- such as future seekers of rental housing, future victims of murderers, future taxpayers, and future consumers." (324))
I am not sure that Posner is right to call "self-control" an emotion, but I do agree that the desire to control oneself is an emotion. As a solution to the problem of the unfairness of (some of) the emotions people actually feel, however, self-control seems unreliable. The problem with it is that the person who must wrestle with himself for control already seems to have lost the battle. So much energy is going into the wrestling that the struggler already can't devote his or her full resources to the issue that calls for judgment. Equally obviously, the person struggling for control is prone to over-correction, and if aware of that, to further efforts to correct for it, all of which take the judge (or person) away from the full body of intuition and experience which is what he or she actually brings to the choices life, or adjudication, requires.
Thus what the judge needs is not so much the ability to control himself or herself, as the state of being in control. One might say, then, that the only way to be a good judge is ... to be, already, a good judge. There probably is some truth to this; it would be one reason (others have more to do with the play of power and career advancement in society) why judges often are older people, who have had the time to reach this state of self-control. But if practical wisdom is a form of expertise, as it seems to be, then like other expertises it can also be practiced, and studied, on the road to mastering it.
While I agree with Judge Posner that "self-control" is one of the virtues of a good judge, however, I think "detachment" may not be. The law and economics judge whom Posner praises is detached from the immediate anguish in front of her, but she is not detached from the desire to promote human wellbeing. She may indeed care deeply about this goal, and perhaps we might call this a "passion for justice." Samuel Pillsbury, in "Harlan, Holmes, and the Passions of Justice," another essay in The Passions of Law, characterizes Justice Holmes as having had this sort of Olympian, detached, passion for justice. (348-49) Pillsbury agrees as well that Justice Holmes may have been too detached from the concrete human details of the cases before him. (352) Pillsbury believes that we need a variety of passions for justice on the courts (351-52), and this is no doubt true. But it is also true that a detachment that puts aside concrete people in favor of abstract human aspirations is, in some measure, an incomplete response to human experience.
Posner may not be arguing for that measure of detachment -- his point may be that the natural response to a concrete situation is to be so gripped by those particulars as to lose broader perspective, so that what is needed is that measure of detachment that enables the judge to see both the specific and the broad. That seems like the right goal, and it also seems like an appropriate way to characaterize the aim of "practical wisdom."