 In the Search at least, Malebranche seems to be thinking that the divine intervention cases provide us with a reason to think that it is God who does all the causal work. For when God intervenes to bring about an effect contrary to what the demon wills, it is clear that God is the unique cause of the event. So parity of reasoning suggests, or so Malebranche seems to be thinking, that in the normal case in which I will my arm to go up and it does go up, it is also God who alone brings about my arm going up. But this argument is far from convincing, since it does not follow from the fact that my power can be overridden in certain circumstances, that I am powerless simpliciter. We still need to consider cases when my power is not overridden, and it seems clear that the fact that I successfully pushed the door shut when my five year old son pulled to open it does not entail that when my son is successful in opening the door with my help, my son is causally ineffective.