PMI (plus, minus, interesting)

PMI—plus, minus, interesting—is a deliberate-attention tool for exploring an idea before deciding whether to accept or reject it. It is especially useful when a suggestion sounds impractical at first, because it separates exploration from advocacy and gives the group permission to notice possibilities that an immediate debate would suppress.

When to use it

• Use PMI to develop a new idea or examine one that is being dismissed too quickly.
• Use it when optimism, pessimism, hierarchy or group consensus is narrowing the discussion.
• Use it in brainstorming to protect contributors from ridicule and keep tentative ideas available for development.
• Do not use it as the final decision method when evidence, risk analysis or specialist judgment is required.

Origins

Edward de Bono developed PMI as part of his programme for teaching thinking as a practical skill. It belongs to his family of attention-directing tools: participants deliberately look in one direction at a time rather than defend an initial position. PMI can filter brainstorming output, but it can also generate ideas in its own right by revealing benefits, drawbacks and intriguing consequences that were not visible in the original proposal.

What it is

The three lenses are:

Plus — potential value, advantages, beneficiaries and enabling conditions.

Minus — costs, harms, constraints, failure modes and people who may be disadvantaged.

Interesting — questions, surprises, second-order effects, experiments and possibilities that are neither simply positive nor negative.

The categories are prompts, not a scoring system. Their purpose is to broaden attention before judgment. A balanced page does not mean the idea is sound, and one severe risk can outweigh many minor advantages.

How to use it

1. State the idea or proposition neutrally, then spend one uninterrupted minute generating only pluses.
2. Spend one uninterrupted minute generating only minuses. Describe risks specifically instead of using vague objections.
3. Ask what is interesting: what would follow, what remains unknown, what could be tested and what new idea has appeared?

A facilitator can combine PMI with brain-friendly brainstorming by alternating focused work and short pauses. Prevent rebuttal while each lens is active; participants may add observations but should not argue them yet. Afterwards, cluster duplicates, identify assumptions and decide what analysis is needed. Convert promising “interesting” items into experiments or questions, and route material risks into proper evaluation.

Final analysis.

PMI works because it interrupts premature certainty. Looking for positives can develop a weak idea; looking for negatives prevents enthusiasm from hiding risk; and the interesting lens captures information that binary evaluation misses. It also makes dissent safer by requiring everyone to examine several directions.

Its simplicity is a limitation as well as a strength. The exercise does not estimate probability, impact, ethics or feasibility, and equal airtime does not imply equal importance. Use PMI to improve the option set and the quality of questions, then make the decision with evidence and accountable judgment.

Top practical tip

Keep the lenses separate and postpone debate. The quality of PMI comes from directing everyone’s attention to the same question before the group evaluates what it found.

Top pitfall

Do not count entries or treat the columns as equivalent weights. A long list of minor pluses cannot neutralise one critical safety, legal or ethical problem.

Further reading

De Bono, E. (2006) De Bono’s Thinking Course: Powerful Tools to Transform Your Thinking. London: BBC Active.