Assumptions are pieces of information that are presumed to be true, often without any evidence to support them.
In Lean, people often resist changes by presenting assumptions as fact. “Our customers will never go for that.” “We need all these parts or the line will shut down.” “We can’t get those two machines closer.”
Time and time again in Lean, assumptions act as an artificial obstacle, holding up progress. Even something like the assumption that a wall has to remain in place can be wrong. Insightful teams have added doors where there were none, or have taken out whole walls. Don’t assume anything in Lean.
When you learn to question assumptions, miraculous things can—and do—happen.