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The Tenth Man Rule: How to Take Devil’s Advocacy to a New Level

Management advice from zombie movies should not be dismissed lightly. They’re all about life-altering decision-making after all. World War Z (2013) illustrates this quite well I think. While the unsuspecting world is overrun by zombies, one nation was prepared for the undead: Israel. What gave them the edge? They had adapted their decision-making to account for an event nobody else deemed possible. They followed the Tenth Man Rule.

The Tenth Man Rule

In the film, the Tenth Man Rule is a strategy Israeli intelligence adopted after they had repeatedly failed to take threats seriously. The Yom Kippur War of 1973 is the prime example of the learning curve. So when they intercepted an outlandish communiqué warning about the undead, a council of ten discussed the matter on different terms:

If nine of us who get the same information arrived at the same conclusion, it’s the duty of the tenth man to disagree. No matter how improbable it may seem. The tenth man has to start thinking about the assumption that the other nine are wrong.

Mossad Chief Jurgen Warmbrunn, World War Z

Sounds gripping and dramatic – as a blockbuster should. But what makes this method worthy of your time? Well, there’s more to the principle than just cinematic effect. The Tenth Man Rule has its origins in devil’s advocacy. So let’s start there.

Devil’s Advocacy

In common parlance, a devil’s advocate is someone who argues against a widely accepted or dominant viewpoint. Usually for the sake of argument alone, given nobody else disagrees. It also means that lucifer’s lawyer doesn’t have to be personally convinced of the contrarian viewpoint. In other words, devil’s advocacy is a way of establishing and steelmanning an antagonistic viewpoint to expose the weaknesses of an idea.

Having said that, it seems like the advocatus diaboli needs a particular type of personality. A proclivity to make unsolicited counterarguments that fly in the face of prevailing opinions is undoubtedly helpful. Relatively low levels of agreeableness and negative emotion are probably required. It also seems to me that being high in openness to experience, that is, having a high interest in ideas, might be beneficial for generating contrarian viewpoints in the first place.

So a devil’s advocate requires not only critical thinking skills but also a willingness and motivation to see and point out precisely the unpopular side of any argument. Whatever position prevails, the contrarian feels inclined to oppose or refute the point being made. In a sense, it’s a form of inverted thinking which opens up a conflict between the individual and the group.

The Grief With Groupthink

No doubt, decisions made by groups can be superior to those made by an individual. Our reasoning is constrained by a myriad of barriers to critical thinking. Collaborative analytic techniques help mitigate our cognitive biases and overcome the limitations of a single mind. However, we also know how group dynamics can lead to bad decision-making. Bikeshedding, for example, makes a group spend more time on trivial issues than on important ones. Though, the most infamous group-related cognitive bias is probably groupthink.

Groupthink is a psychological phenomenon popularised by Irving Janis in 1982.[1] He illustrated the concept with case studies from foreign policy disasters such as the 1961 Bay of Pigs Invasion. We might even say World War Z echoes Janis’ work on national security intelligence and the reasons for its failures.

We can conceptualise groupthink as pathological social conformity. On the one hand, you’d want your group to be cohesive, cooperative and harmonious. On the other hand, there’s a necessity for disagreement when the group has to address an uncomfortable and severe problem. Unfortunately, groupthink can cause members to agree with one another for the sake of not creating conflict within the group. The harmony comes at the cost of critical thinking and evaluation of the facts.

So the group is certainly not always right.[2] Members might disagree, but the dissent could be suppressed and invisible; through self-censorship or rationalisation. This is where the devil’s advocate comes in. It’s the individual who dares to rise above the group and say what nobody else has thought of or wants to say out loud.

Advocatus Diaboli Institutionalem

Granted, all this is not new. Organisations have long used a form of devil’s advocacy to help good decision-making along. Most famously the Catholic Church of course. Rome used to employ the advocatus diaboli to do a thorough background check on those who were poised to be named saints. It was the church’s equivalent to examining your Twitter feed for Wrongspeak if you will. Institutionalising the position and awarding it to someone with the appropriate qualifications took chance and serendipity out of the equation.

Even beyond the church and the intelligence community, quasi-institutionalised versions of the advocatus diaboli are fairly common. Take education for example. At least nominally, it has a built-in devil’s advocacy. A good politics class is about political decision-making and students learning how to come to an independent judgement. “If there’s no controversy, it’s not a politics class”, my teacher trainer used to say.

It’s the educator’s job to establish viewpoint diversity on any issue, tease out different opinions from students, or provide counter-arguments if everyone else agrees. Similarly, this is what most debate games and contests are all about. It’s often an obligatory requirement for debaters to take a viewpoint with which they don’t agree.

Lastly, companies have also long discovered the benefits of making “critical thinking and contrarian viewpoints part of the process” [3] to combat groupthink. The thinking here is very similar. Give a person or team within the group a mandate to test and possibly falsify a claim or idea. Whatever decision is made in the end, so the rationale, it will be strengthened by having it intentionally challenged.

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While the concept of institutionalised devil’s advocacy gets us closer to the Tenth Man Rule, I don’t think having a designated professional pain in the neck is a guarantee for good decisions.

The Devils and the Details

Introducing somewhat artificial, mandated and extreme forms of dissent can have negative side effects. As with all directives, you shouldn’t underestimate the art of following rules by breaking them. Several potential lines of conflict may emerge in an organisation:

  • Where do you draw the line between constructive dissent and annoying nitpickery?
  • What happens if devil’s advocacy becomes destructive, leaving decision-makers with no viable option and stifling their ability to act?
  • How much of your limited resources are you willing to use? How outlandish does an objection have to be before it’s considered a waste of time?
  • How do you avoid unprincipled devil’s advocacy that harms group cohesion to an unacceptable degree?
  • How prepared is everyone to have their assumptions challenged?
  • How are you going to handle the potential emotional fallout of wounded egos if ideas keep being shot down?
Elephant In the Room

It seems like institutionalised devil’s advocacy can easily degrade into a performative tick-the-box exercise that will defeat its original purpose. If people begin to feel that it only benefits the devil, it could lead to a positive feedback loop. In its end, you have informal social sanctions for anyone who takes this whole devil’s stuff too seriously. Think of it as an auto-immune reaction of the group to ostracise Lucifer’s lawyer.

Probably to the surprise of no one, success hinges on the internal culture. The worst organisations seem to be those that proudly proclaim a culture of devil’s advocacy but practice it as mere lip service. Those are places where virtue is punished, where objections are invited but never acted on or informally sanctioned. The best ones, on the other hand, are places such as High Reliability Organizations. Those are places operating in high-risk environments where constructive dissent is rewarded even when you turn out to be wrong. Oddly enough, those are organisations where lives are at stake every day.

The Benefits of The Tenth Man Rule

With all that said, how’s the Tenth Man Rule any different then and when should it be used? Let’s first outline again what the Tenth Man Rule says:

  • In a group of ten, everyone is given the same information.
  • If nine group members come to the same conclusion, the tenth person becomes the devil’s advocate.
  • The tenth person is now responsible for disproving the others.
  • The improbability of the hypothesis that everyone else is wrong is no factor.

Admittedly, the details have to be fleshed out a bit more. It’s not entirely clear what counts as the “same conclusion” in different scenarios. Also, the mechanism of how to determine the “tenth” person needs a bit more explaining. It certainly can’t be going around the table always asking the same poor guy last. But let’s steelman the idea in five points:

  1. The table of ten is round, meaning everyone is equal. There’s no hierarchy, so nobody has an information advantage.
  2. There’s not one designated devil’s advocate. Instead, there’s convenient randomness to the process which pre-empts groupthink. Everyone could become the devil’s advocate on any issue (and probably has in the past), so there’s less incentive to agree by default.
  3. Even if everyone genuinely agrees, there’s always a person who will act as a fail-safe for viewpoint diversity. Again, given that the advocatus diaboli likely changes with every issue, it introduces an aspect of reciprocity.
  4. The deliberate inclusion of improbable events makes it less likely that Black Swans are overlooked.
  5. Commitment to devil’s advocacy on an issue is intended as thorough and long-term. This keeps it from being a tick-the-box exercise.

Putting the Tenth Man Rule in Perspective

The Tenth Man Rule seems to be able to balance group cohesion with individual dissent. But I’ll admit, it also sounds like a resource-sucking strategy that should be reserved for zombie apocalypses and other high-stakes decisions. Good luck making it a board member’s life mission to prove your organisation made the wrong choice with the new coffee machine. It also seems to rely very much on group members having the appropriate expertise.

There’s one remaining issue, though. A cynic might say that everyone wants you to think critically until you actually do it. If the Tenth Man Rule is used for high-stakes decisions, it has to hold its weight with even the most emotionally charged topics. Just think of your field’s equivalent to climate change, vaccinations, or gun control. In short, any issues that touch on or question your most internalised values. There’s a reason why the advocatus diaboli is speaking for evil personified.

But the Tenth Man Rule also needs a limiting principle so the group is not paralysed by eternal disagreement. In my mind, this requires a set of shared axiomatic truths, such as a common epistemology and sense-making method. At some point, the devil’s advocate will have to concede that his or her assumption about the others being wrong is false.

While shared values can be declared, I don’t think they can be imposed on the group in a top-down fashion. I also don’t think group cohesion is reliant on avoiding the tough questions. Instead, culture is built and continually negotiated by successfully working through difficult conversations, ethical conundrums and decisions.

Closing Thoughts

To channel Monty Python’s Argument Clinic, devil’s advocacy is all but an automatic game of mere contradiction. Mephisto’s mouthpiece must know how to disagree. Preferably, in a substantive, informed and constructive way. These are valuable skills to cultivate within any organisation. If they’re sacrificed to groupthink, someone outside of the group will play that role and chances are, they don’t have your best interests in mind.

If we wanted to take this idea yet another step further, we’d have to consider Red Teaming. Red Teaming is a more sophisticated form of devil’s advocacy that puts a team in the shoes of your competitors to stress-test anything you do. As opposed to traditional devil’s advocacy, the red team operates clandestinely and uses any means at their disposal.

As for World War Z, the only reason we learn about the rule is that the tenth man successfully disproved the other nine. Israel prepared for the unlikely contingency, and it worked out for them. (Kinda.) So don’t take advice from zombie movies too lightly. How are you going to avoid your equivalent of a zombie apocalypse?

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