Get New Ideas by Email. Join 3k+ Readers.

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

Management advice from zombie movies should not be dismissed lightly. Ultimately, they’re all about making life-altering decisions. A concept from the 2013 zombie film World War Z illustrates this perfectly. While the unsuspecting world is overrun by the undead, one nation is prepared: 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.

What Is The Tenth Man Rule?

The Tenth Man Rule suggests that, if nine people in a group of ten agree on an issue, the tenth member must take a contrarian viewpoint and assume the other nine are wrong. In World War Z lore, it’s the strategy Israeli intelligence adopted after their repeated failure to take highly unlikely threats seriously. The Yom Kippur War of 1973 is the prime example of this learning curve. So when they intercepted an outlandish communiqué warning about the undead, a council of ten got together to discuss 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 suspenseful — as a blockbuster should. But what makes this method worthy of your time? Well, there’s more to the principle than drama. The Tenth Man Rule has its origins in devil’s advocacy. So let’s start there.

The Nature of Devil’s Advocacy

In common parlance, a devil’s advocate is someone who argues against a widely accepted or dominant viewpoint. Often for the sake of argument alone, given nobody else disagrees. Devil’s advocacy also implies 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 stance 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 making unsolicited counterarguments that fly in the face of prevailing opinions is undoubtedly helpful. If we think in terms of the Big Five personality traits, relatively low levels of agreeableness and negative emotion are probably required. It also seems like 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 more than just critical thinking skills. He or she needs the courage, willingness and motivation to see and point out the unpopular side of an 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 plays with the eternal 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 analytical 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. The most infamous group-related cognitive bias is probably groupthink.

Groupthink is a psychological phenomenon popularised by Irving Janis in 1982. The more coherent a group is, the higher the probability that they will sacrifice critical thinking on the altar of group cohesion. Janis 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.

It’s tricky. On the one hand, you want your group to be cohesive and cooperative. On the other hand, there’s a necessity for healthy disagreement when the group has to address complex problems. Unfortunately, groupthink can cause members to agree with one another for the sake of not creating conflict within the group. This harmony comes at the cost of a critical evaluation of the facts.

So the group is not always right either. While there will almost certainly be some level of disagreement, dissent could be suppressed and invisible. Through personal rationalisations or self-censorship. 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.

Institutionalised Devil’s Advocacy

Clearly, the Tenth Man Rule is not entirely new. Organisations have long used a form of devil’s advocacy to help good decision-making along. The Catholic Church, who gave it its name, employed the advocatus diaboli to do a thorough background check on those who were poised to be named saints. It was the church’s equivalent of HR scrutinising your Twitter feed for Wrongspeak. Institutionalising the position systematised the whole approach.

Beyond the church, quasi-institutionalised versions of the devil’s advocate 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 the opinions of the students and provide counterarguments to challenge them if necessary. Similarly, this is what debate games are all about. It’s often an obligatory requirement for debaters to take a perspective with which they don’t agree. As Mill’s Trident suggests, having your viewpoint challenged is always beneficial. Whether you’re completely wrong, partially right or entirely correct.

Lastly, companies have long discovered the benefits of making “critical thinking and contrarian viewpoints part of the process” to combat groupthink. The rationale is similar: to give people a mandate to test and possibly falsify a claim or idea. Whatever decision is made in the end, it will be strengthened by having it intentionally challenged. Though, I don’t think having a designated professional pain in the neck is a guarantee for good decision-making.

The Devils and the Details

Introducing somewhat artificial and mandated forms of dissent can have unintended consequences. They may open up a whole new world of internal power games. Several potential lines of conflict may emerge in an organisation:

  • Where do you draw the line between constructive dissent and unprincipled nitpickery?
  • What happens if your 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 to pursue further?
  • 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?

Even 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 the exercise only benefits the designated devil, it could undermine trust in the whole process. In the 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.

Organisational success hinges on internal culture. The worst organisations seem to be those that proudly proclaim a culture of challenging each other’s viewpoints but practice it as mere lip service. Those are places where objections are invited. But they’re never acted on or informally penalised. The best organisations, on the other hand, are places such as High-Reliability Organisations. Where constructive dissent is rewarded even when the critic turns out to be wrong.

The Tenth Man Rule In Practice

With all that said, how is the Tenth Man Rule any different? And how could it be used effectively? Let’s first remind ourselves 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 devil’s advocacy is triggered regardless of how improbable it may seem that everyone else is wrong.

We don’t get much insight into how this process unfolds in practice. As always, the devil is in the details. 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 exploration. It certainly can’t be going around the table always asking the same poor guy last. But I think there are a few more principles implied in the rule:

  1. The table of ten should be round, meaning everyone is equal. There’s no formal hierarchy, so nobody has an information advantage. This also suggests that members must be highly qualified master thinkers. People who can keep up with each other; both intellectually and in terms of integrity.
  2. There’s not one designated “tenth man” either. Instead, we must establish a convenient randomness to the process. 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. However, the group would almost certainly only convene if the issue is considered a Black Swan. That is a highly improbable event with a potentially severe impact.
  4. Commitment to being the devil’s advocate for a position is intended to be thorough and long-term. The tenth man might spend years chasing that Black Swan. This prevents it from being a short-lived tick-the-box exercise.
  5. 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. Each member may be an active devil’s advocate, albeit on a different issue.

Now that the details have been fleshed out a bit more, let’s turn to the challenges the Tenth Man Rule presents.

Challenges of The Tenth Man Rule

Elephant in the Room
Hidden Wisdom

First of all, the Tenth Man Rule needs a limiting principle. The group cannot be paralysed by eternal disagreement. In my mind, this requires a set of shared values and sense-making methods. At some point, the tenth person must present his or her conclusion. At some point, the devil’s advocate may have to concede that his or her assumption about everyone else being wrong is false.

Second, as I pointed out above, the Tenth Man Rule sounds like a resource-sucking exercise 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. (Read more about Bikeshedding if you think this scenario is too far-fetched.)

Thirdly, we might take a cynic’s perspective and say that everyone wants you to think critically until you actually do it. If the Tenth Man Rule is used for high-stakes decisions, members have to commit to honouring it even when it comes to the most emotionally charged topics. Just think of climate change, vaccinations, or gun control. Members of a tenth-man council must be prepared to spend years of their life working under the assumption that their most deeply ingrained personal beliefs are false.

Alternatives to The Tenth Man Rule

The Tenth Man Rule aims to balance out pathological group cohesion with heroic individual dissent. I exaggerate of course. But this way of thinking about the method shows why there are probably better alternatives. Truth be told, the tenth-man method is adversarial in nature and relies an awful lot on a single steadfast individual.

If we wanted to reap the benefits of a contrarian method while not relying on one person, we could consider Red Team Analysis. Red Team Analysis is a form of devil’s advocacy that puts a team in the shoes of a competitor. The goal is to find and exploit your weaknesses; for example in your business model. As opposed to traditional devil’s advocacy, the red team operates clandestinely. Done right, it can create healthy competition. Between those who aim to make the best decisions. And those who aim to show why the decisions are not the best.

A final alternative is Premortem Analysis, a more collaborative analytical technique designed to anticipate failures. Shortly before a decision is reached, the group is tasked to imagine themselves in the future. Their decision has turned out to be spectacularly mistaken. They ask themselves: What went wrong? As with the other methods, Premortem Analysis not only encourages dissent, it legitimises it. Only this technique turns the entire group into critics of their own process and its outcome. Now, being critical aligns with the group’s own goal.

Closing Thoughts

The Tenth Man Rule is surely an unconventional way to find weaknesses in an organisation’s decision-making. But it’s not about mere contradiction. Mephisto’s mouthpiece must know how to disagree in a substantive, informed and constructive way. If critical thinking is sacrificed to groupthink or blind contrarianism, an outsider might expose those weaknesses. And chances are, they won’t have your best interests in mind.

As for World War Z, the only reason we hear about the rule in the film is that the tenth man successfully challenged the other nine. Israel prepared for the highly unlikely high-impact event and it worked out for them. (Well, kind of.) So don’t take management advice from zombie movies too lightly if you want to avoid your equivalent of a zombie apocalypse.