Great Inertia is the tendency of human systems to preserve familiar meaning, assumptions, relationships and ways of acting, even when changing conditions require adaptation.
Organisations need stability. Shared routines, structures and understandings enable people to coordinate, build trust and act coherently. But the same forces that create stability can also preserve assumptions and behaviours that no longer fit reality.
This helps explain why organisations can appear to change while remaining much the same underneath. Strategies, structures, technologies and processes may change while established mental models continue shaping how people interpret problems and make decisions. Under pressure, familiar patterns can readily reassert themselves.
Great Inertia is therefore not simply resistance to change. It is the tension between preserving enough coherence to act together and remaining sufficiently open to learn when reality changes.