Klein's pre-mortem inverts retrospective analysis: before a decision is committed, the team imagines themselves a year in the future, with the project having ended in disaster. Each person privately writes down why it failed. Because the premise is settled — failure happened — people who hesitated to voice doubts feel safe to articulate them. The technique reliably surfaces 30% more failure modes than open 'what could go wrong' brainstorming.
The principle: Pessimism phrased as fact is heard more cleanly than pessimism phrased as opinion. Move the question from 'might it fail' to 'why did it fail' and the silent worries become visible.