The lean mindset, as articulated by mary-poppendieck and tom-poppendieck in the-lean-mindset-2013, is the meta-principle that underlies all lean practices: developing the expertise to ask the right questions, solve the right problems, and do the right thing in the situation at hand. Where the seven-lean-principles provide a framework for action, the lean mindset is about the cognitive orientation that makes those principles work.
This concept represents the Poppendiecks' mature position that lean is fundamentally a mindset — a way of thinking — rather than a set of tools or practices. Organizations that adopt lean practices without developing lean thinking will inevitably revert to old patterns, because the practices are expressions of the mindset, not substitutes for it. This echoes w-edwards-deming's insistence that transformation requires "profound knowledge" — not just new techniques but a new way of seeing the system.
The lean mindset concept also connects to growth mindset research (Carol Dweck) and Toyota's kata practices (Mike Rother's "Toyota Kata"), both of which emphasize that capability develops through deliberate practice of problem-solving routines, not through memorizing solutions.