The action of opening a door by pushing on it is composed of the agent's action of voluntarily exerting force with his or her arm and hand plus that action's causing the door to open. Is the voluntary exertion of arm and hand similarly composed of an action producing a result? There is a clear candidate here for the role of result—namely, the limb's exerting force. It could have exerted exactly the same force, by means of just the same muscle contractions, without the agent's voluntarily exerting the force with it. So the exerting of force by the limb is only a part of the whole action. But does the remainder consist of this part's being caused by action of the agent? Philosophers disagree on the answer to this question. Section I below offers one way of spelling out an affirmative answer (which is developed more fully...