Okay, we all know about James Reason's Swiss Cheese model.
It has been done to death a million times over on Pprune. His point is that pilots are never to blame for accidents and that by his account command responsibility is an old fashioned irrevelant term. Some may find this hard to digest but pilot error is often the direct cause of an accident and all the Swiss Cheese holes have little to do with it. But one thing is certain and that is Professor Reason had made a bucketful of money with his theory.