Tool/Mental Model/No. 0754

Pre-Mortem

Imagine the plan has already failed, then explain why. You’ll find problems you couldn’t see while hoping it would work.

Also called Pre-Mortem Analysis · Premortem · Prospective Hindsight

a tool: pick it up

Evidence: Useful, modest evidence
Read: 5 min
Links: 18 connections
Useful when: Deciding under uncertainty · Estimating time and cost · Group decisions and meetings · Risk and safety · Running projects

01You've seen this when…

at work
Before a launch, someone asks “What are the risks?” and the room offers three polite bullet points. Ask “It’s six months later and this flopped. What happened?” and the same room fills a whiteboard.
in life
Before moving city for a job, you picture yourself a year later, unhappy, and ask why. The answers, like no friends nearby or an hour-long commute, are things you can plan for now.
out in the world
Festival organizers imagine tomorrow’s headline, “Festival ends in chaos”, and work backwards. A crush at the single exit, an overloaded mobile network, a heatwave.

02The idea

Before a plan is final, gather the people involved and say: It’s a year from now. We went ahead with this, and it failed badly. Take a few minutes and write down every reason why. Then collect the reasons and use them to make the plan stronger.

This sounds like asking “What could go wrong?”, but it works differently. “What could go wrong?” invites people to defend the plan, and to sound supportive. Declaring the failure as a fact changes the task from defending to explaining. People are much better at explaining something that happened than at imagining something that might.

Researchers call this prospective hindsight. Their studies suggest that what helps isn’t the time travel. It’s treating the outcome as certain. Explanations for a sure outcome come out longer and more specific.

It also gives permission. In a pre-mortem, finding the flaw is the assignment, so raising it counts as doing the job well. The overconfidence and groupthink that settle over an agreed plan are suddenly the thing being tested.

03How to use it

Pick the moment. After the plan is broadly agreed, before you commit money, people or an announcement.
Set the scene concretely. “It’s March. We launched. It was a disaster.” The more specific the imagined failure, the better the reasons.
Write alone first. Two to five minutes of silent writing, so the first or most senior voice doesn’t anchor everyone else.
Go round the room. One reason per person per turn, until the lists run dry. Write everything down without debating it yet.
Sort and act. Mark which reasons are likely and which would be fatal. For the top few, change the plan, add an early-warning signal, or agree a point at which you’d stop.
Put the warning signs in the calendar. Give each one a date and a person who checks it.

Working alone? Write a short letter from your future self explaining what went wrong.

04A worked example

A team plans to migrate the company’s billing system over a weekend. The plan has been reviewed and everyone feels confident. They spend thirty minutes on a pre-mortem: “It’s Monday morning. Billing is down and some customers were charged twice. Why?”

The reasons that came out:

The rollback had never been tested end to end.
A finance export job runs at 2 a.m. on Sunday, and nobody on the migration team owns it.
The only person who understands the tax module is on holiday that week.
The status page depends on the system being migrated, so customers wouldn’t be told.

None of these were in the risk register. Two changed the plan: a full rollback rehearsal on staging, and moving the window away from the export job.

What made it work The failure was stated as fact and people wrote alone before talking. Then each reason that mattered got an owner and an action.

05When to reach for it

Everyone agreed to the plan quickly.
The decision is expensive or hard to reverse, a one-way door.
The people reviewing the plan are the people who designed it.
Risk discussions keep producing generic answers like “timeline” or “resourcing”.

06When it misleads

It becomes theater. A long list is produced and nothing changes. Tie each top reason to an owner and an action.
It’s too late. Once a decision is announced, people defend it instead of examining it.
It only finds failures you can imagine. Your imagination is limited by your experience. Pair it with the outside view: how did similar projects actually turn out?
It can make you timid. If every imagined failure is treated as likely, good plans get killed. Rank reasons by how likely and how severe they are.
It depends on candor. If it’s the boss’s pet project, people self-censor. Anonymous writing helps.

07Roots

The name flips a medical ritual. A post-mortem examines a body to learn why the patient died. Its lessons arrive too late for the patient on the table. Gary Klein wanted the same lesson while there was still time to use it.

Klein is a psychologist who spent his career studying how firefighters, soldiers and nurses make decisions under pressure, watching them at work. The technique he built rests on a 1989 study by Deborah Mitchell, J. Edward Russo and Nancy Pennington. They asked people to explain events framed either as uncertain or as already settled, and found that treating an outcome as certain produced richer, more specific explanations. They called it prospective hindsight.

Klein’s team turned that finding into a meeting format and used it with project teams before describing it for managers in the Harvard Business Review in 2007. It spread much further after Daniel Kahneman recommended it in Thinking, Fast and Slow as a cheap counterweight to the optimism that settles over a group once a plan is agreed.

08How solid is this?

The mechanism is well supported. People generate more and better explanations for an outcome they treat as certain. A study of planners found pre-mortems reduced overconfidence about twice as much as listing pros and cons. There’s little rigorous evidence yet on whether projects that run pre-mortems actually fail less.

10Origin and sources

Gary Klein (2007), building on research into “prospective hindsight” by Deborah Mitchell, J. Edward Russo and Nancy Pennington (1989). Popularized by Daniel Kahneman in Thinking, Fast and Slow (2011).

[1]Klein, G. (2007). Performing a project premortem. Harvard Business Review, 85(9), 18–19.
[2]Mitchell, D. J., Russo, J. E., & Pennington, N. (1989). Back to the future: Temporal perspective in the explanation of events. Journal of Behavioral Decision Making, 2(1), 25–38.
[3]Veinott, B., Klein, G. A., & Wiggins, S. (2010). Evaluating the effectiveness of the PreMortem technique on plan confidence. Proceedings of ISCRAM 2010.
[4]Kahneman, D. (2011). Thinking, Fast and Slow, chapter 24. Farrar, Straus and Giroux.

Suggest an edit· Updated 2026-10-01