We do many things by doing something else. You might move across the room by walking and walk by moving your legs. But do you move your legs by doing something else? You might think, yes: by sending nerve impulses from your brain. And maybe you do that by sending around other such things in your brain? But are “you” really doing those things that happen in parts of you?
The priest and philosopher Nicolas Malebranche argued that no-one can really do anything themselves because in order to do something, you need to know how to do it — and we don’t know how to cause all that neural stuff that needs to happen for our bodies to do anything. (He thought God is really the one who does everything.) This isn’t a good argument. To know how to do something must mean knowing how to do that something by doing other things (eg. how to move your hands and fingers while playing the piano). So if you must always know how to do everything, then you must know how to do the things by which you do that other thing: how to make your fingers move, and then probably how to send those neural signals, and then how to do whatever you do to do that; it’s an infinite regression. To make the regression stop, there must be some things we just can do, so that we can do more complex things by doing those things.
Anyway, it’s not really true that to do something, you must know how to do it. It is usually true to say that “if you don’t know how to do something, you can’t do it.” But that’s because if you’re saying you don’t know how to do something, you’re probably thinking of a case in which you do need to know how to do the thing in order to do it. Knowing doesn’t always come into it at all. If you just have the ability to move your fingers, you don’t need to know how they work, you still have the ability.
Malebranche could still have some kind of a point abut God, just said in different words, but enough of him. The above is just to show that it seems we need to think in terms of some kind of simple actions that we just can do. Arthur C. Danto called these basic actions in his essay by the same name “Basic Actions”. They are the actions you don’t do by doing anything else. You just have the ability to do them by willing it. So, again, you might be able to walk across the room by walking, and walk by moving your legs, but you are just able to move your legs.
There’s something funny about this level of description. If we can analyse that the walking was done by these movements of the legs, why can’t we say that the movements of the legs were done by these movements of the muscles being caused by these neural signals. If we knew exactly how everything happens, surely we wouldn’t have to stop before we are at the deepest level of physics, the “theory of everything”? (If there is such a thing.)
We could go on deeper in the description, that’s true. But there are reasons why we might not want to when explaining events as actions taken by humans. The above discussion already shows some of the reasons why.
If we talk about what a person does but go below the level where the person acts as a whole — instead talking about their nervous system or muscles — we can no longer “see” the person as part of that description; we move into an impersonal description. That may be fine, but it’s not usually what we want at this point. Additionally, as seen above, when we are talking about how to do something, there is no point in going below the level where a person is capable of just doing things, like moving their limbs, by willing it. There is a certain line, though it may not be completely absolute, below which a person simply experiences what they do as something they can do but not usually explain. They see themselves as a whole with the capacity to do these things, and so usually do we from the outside.
Thus, it makes sense to speak of basic actions even though they are not so basic that you could not go beyond them in explanation. If you do go beyond, you are losing sight of human agency and the human way of understanding our own actions. Human beings are not indivisible wholes, but often it is useful to think of them as such.