A brief item in the New York Times offers an intriguing antidote from ancient history to the timeless problem of subtly enforced conformity of opinion.

One of the most influential theories in the behavioral sciences in recent decades is “groupthink.” Developed by the psychologist Irving Janis in the early 1970s, the groupthink theory describes how a tight-knit, smart and well-informed group can suppress dissent and make disastrous decisions because of the pressure to agree.

Hm, that sounds familiar. But isn’t consensus in a given community of experts — on, for example, the scientific question of Darwinian evolution — supposed to be a guarantee that the unanimous experts are right?
Yeshiva University psychologist Eliezer Schnall presented a paper earlier this month to the American Psychological Association noting some of Janis’s historical illustrations of groupthink at work, such as the failure among American political leaders and the intelligence community to foresee the Japanese attack on Pearl Harbor. In Schnall’s view, the wise men of ancient times were sensitive to the possibility that a consensus could mask the psychological dynamic where intelligent decision making is distorted by the pressure to conform.
The Jewish high court, as Schnall discussed in his presentation — that is, the Sanhedrin, comprising 71 judges — had an interesting remedy to this danger. If a decision in a court case was unanimous, with all judges in agreement and forming a perfect consensus, the decision was automatically set aside and rendered null and void. The validity of the decision was assumed to be tainted by the agreement of all the experts sitting in judgment.
A consensus, in this view, is far from a guarantee that the truth has been discovered. On the contrary, it’s an indication that groupthink is afoot.