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WHAT: The Tenth Man Principle (aka The Devils Advocate) is the 10th and final rule of the “BS Detection Kit“. It is a contrarian way of coming to a decision based on a skeptical view of consensus: “if ten people are in a room, and nine agree on how to interpret and respond to a situation, the tenth man must disagree. His duty is to find the best possible argument for why the decision of the group is flawed.” (R2)

WHY: In many group-think situations consensus relies on conformance to principles and processes where flaws are either ignored or not recognized. The tenth man is loyal opposition who is an expert in those principles and processes so their flaws can come to light: “Our systems badly need loyal opposition– not mere contradiction…. A loyal opposition has the common good front of mind; it shares the ends but purposefully dissents on the means. A loyal opposition is not a contradiction in terms, but rather the promise of clear decision making and accountability.” (R1)

EXAMPLE: The most widely used example is the addition of a Military Intelligence Control Unit within the IDF (Israeli Defense Forces) tasked specifically with challenging widely held assumptions which caught the IDF off-guard during the 1973 Yom Kippur War: “Israel’s Directorate of Military Intelligence (Aman) was almost completely aware of Arab war plans by mid-1973. But following assumptions about the unlikelihood of an Arab alliance,… Aman remained confident that the probability of war was low.” (R1) They ignored information from reliable sources including the CIA, which led to one of the largest military intelligence failures of the 20th Century.

References:
(R1) https://www.cpjustice.org/public/capital_commentary/article/264
(R2) https://www.acesconnection.com/blog/the-tenth-man-principle
Pic: https://rajathathablog.blogspot.com/2018/10/the-boon-that-tenth-man-asked.html

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