As outlined in VI.7, our strategy is to approach the mind from the outside inwards. In other words, we want first to discuss the fundamental capacities for perception and action which form (so to speak) the input and output interfaces between the mind and the world, before we go on to deal with the more purely internal workings of the mind, such as beliefs and desires, sensations and thoughts. Having discussed perception at length in the last two chapters, we now turn to consider the topic of action.

Not everything you do is an action in the sense we are going to be interested in. You move your eyeballs when asleep, you perspire and digest your food, you occasionally lose some hair, you grow older and eventually die: and while these are all things you can be said to do, they will not count as actions in the full-blown sense that is our concern here. An action in our stricter sense is something which is – so to speak – up to you; within limits you have some choice about whether to do it or to refrain. For example, it is up to you whether or not you move your arm or start running, open the door or saw the logs, wake the baby or commit adultery. It is not in the same sense up to you whether you move your eyeballs while asleep; you just have no choice in the matter – your eyeballs move whether you want them to or not.