What is a pre-mortem?

A pre-mortem assumes a decision has already failed and works backwards to explain why. Rather than asking whether a plan might fail — which invites defence — it treats the failure as established and asks for the cause, which makes risks available that the deciding mind would otherwise suppress.

How is this different from a post-mortem?

A post-mortem examines a failure that has occurred, when the cost has already been paid and the analysis can change nothing about the decision itself. A pre-mortem performs the same examination before commitment, when the findings are still able to alter the outcome.

Pre-Mortem: What It Is and How to Run One

What this is

A pre-mortem inverts the post-mortem. Instead of examining a failure after it happens, you assume the failure has already happened, and work backwards to find why. The inversion matters because it changes what the mind is permitted to see: asked whether a decision might fail, a person defends it; told it has failed and asked to explain, the same person produces reasons they were unable to name a moment earlier. It is the only decision tool that pays you to argue against yourself.

The difficulty with examining a decision you have already made is that the examination is conducted by the person who made it. Every question you ask is answered by the part of you that has an interest in the answer. This is not dishonesty. It is the ordinary architecture of a mind protecting a conclusion it has already reached.

The pre-mortem works by removing the thing being protected. If the decision has already failed — if that is the premise, not the question — then there is nothing left to defend, and the reasons become available. People who could not name a single serious risk five minutes earlier will produce four, specifically and without hesitation.

The output is not a prediction. It is a list of the assumptions that were carrying more weight than anyone had noticed.

One further use: the artifact this produces is worth sharing with the person who will bear the decision's consequences alongside you — a co-founder, a partner, a board. Not to persuade them. To find out whether the failure story you wrote is the same one they would have written.

The instrument

The decision, named plainly.

Common questions

What is a pre-mortem?: A pre-mortem assumes a decision has already failed and works backwards to explain why. Rather than asking whether a plan might fail — which invites defence — it treats the failure as established and asks for the cause, which makes risks available that the deciding mind would otherwise suppress.
How is this different from a post-mortem?: A post-mortem examines a failure that has occurred, when the cost has already been paid and the analysis can change nothing about the decision itself. A pre-mortem performs the same examination before commitment, when the findings are still able to alter the outcome.