The history of cognitive decline on the high court teaches two lessons. First, there is a real risk of a substantial time lag between the onset of mental deterioration and a justice’s retirement. But second, and as important, this is a risk that can be contained. No justice—no matter how deranged—can do serious doctrinal damage without the acquiescence of at least half his colleagues. And when a justice is so utterly incapacitated that he is unable to break 4-4 ties, the court can continue to function with an even number of active members. Originally, the court had only six justices; during the Civil War, it had 10; and it has functioned fine with eight members during prolonged vacancies. Indeed, there are notable virtues to having an even number of justices—one of them being that it then takes more than a knife’s-edge majority to overturn a lower court decision or strike down a law nationwide.

The proposed solutions to “mental decrepitude” on the Supreme Court each come with flaws of their own. A common proposal is to fix the lengths of justices’ terms, with 18 years being the number most often suggested. Yet 18-year terms would not lay to rest the problem of mental decline. Murphy had been on the court for only eight years when his apparent drug dependence reached its height. Whittaker finally suffered a nervous breakdown less than five years into his term. And the Rehnquist pajama incident occurred just nine years into his 33-year tenure. Granted, the risk of mental disability increases with advanced age, and 18-year term limits might on balance lead to a younger bench. Or they might not. Presidents might be inclined to select older nominees if justices could serve for only 18 years rather than for life.