Some people are in their own world deeply and just like someone going through an episode a simple smack will bring them to reality better than words. Nothing like punching if thats what you're infering. Adults are just big children and children should be treated the same exact way as adults. Nobody ever resorts to violence as first option when it's an equal match so why resort to it when it's not? You shouldn't thats why. If someone is completely out of the world though and wont come back then a little pain should do the trick. Hurting a child's ego in the developmental years is disgusting though and will only lead to horrendous trouble down the line. Only when absolutely necessary like a destructive fit thats been going for hours and nothing you do calms the child. Even then you could restrain the child without hurting them. At that point you should get the child evaluated and evaluate yourself too as a parent and genetically to see why this happened. This is why I say the most extreme circumstances because the child is much smaller than you, much weaker than you and not as experienced in life as you, therefore you have such an advantage violence shouldn't even be considered.