 The former says that there is one and only one object which is a present King of France and this object is not bald; i.e., there is exactly one present King of France and he is not bald. This reading is false, given that there is no present King of France. The latter says it is not the case that there is exactly one thing that is a present King of France and that object is bald. This reading is true because there is not even one present King of France. 