Combines Chris Argyris's ladder of inference (Overcoming Organizational Defenses, 1990), as set out in The Fifth Discipline Fieldbook (Peter M. Senge, Art Kleiner, Charlotte Roberts, Richard B. Ross, and Bryan J. Smith, 1994), with the Five Whys of Sakichi Toyoda and Taiichi Ohno (Toyota Production System, 1978).
Walks a conclusion back down the ladder of inference and asks why at each rung, producing a list of the assumptions a position rests on.
When to reach for it
When a decision feels right or wrong but nobody can say why, or two sides argue about facts while really disagreeing about assumptions.
How it runs
- Write down the conclusion or position under audit.
- Trace it down: belief, conclusion, assumption, meaning added, data selected, data observed.
- Ask why at each rung until the answer cannot be justified further.
- Mark the assumptions that would sink the conclusion if false.
- Decide how to test each of those before committing.
Where it sits in SOLVE eX
Go to the source
- Overcoming Organizational Defenses, 1990
- Toyota Production System: Beyond Large-Scale Production, Japanese original 1978; English edition 1988, 1978
- The Fifth Discipline Fieldbook, the Ladder of Inference chapter by Rick Ross, 1994