Do we really want to get into defining "reasonable force"? Is it reasonable to hit a child with a belt but not with the cord of an electric jug? Do we want to have in law that we can hit our children with an open hand but not a fist? If the hitting doesn't result in bruising is that ok, but if there is bruising then is that unreasonable? The point I keep coming back to (and it's a point that Russell made in his original blog entry) “is there in fact a good justification that we should sanction - in whatever detail - an act against a child that we would not sanction against an adult?”.