As with any other ways of working with horses, NH has some great aspects. However, a dear friend who has 5 horses and works strictly with the Parelli method had a horrible thing happen with one of her horses. She'd unloaded him, and left him ground-tied, letting him make the right decision (this is a very intellegent woman who has had horses for decades, trained and rehabbed more that a few). He heard some horses calling out, took off, and ran through 3 fence lines, cutting to the bone on chest, front and hind legs. He's a beautiful grey Arab, and she spent months working with him. He's fine now, but has terrible scars. We do not think or see like horses, and cannot always expect them to make the right choices. Possibly I have the concept wrong, but I know what I saw, and the devastation both with the horse and my friend.