How do you get someone unfamiliar with (or disbelieving about) Montessori (and this "strange" idea of self discipline in children) to see that just maybe what you're saying does make sense? What I call "The Playground Effect" is one way, because it connects to almost anyone's personal experiences!
So what REALLY is the explanation for why a solid can be rigid, elastic or plastic? As I revised and rewrote the Geography Activity (Command) Cards, with one aim being the provision of scientific explanations, this is something that I had to look into. It all comes back to those particles ...