Think of the self as a function, not any particular return value. Stuff comes in, stuff goes out; the self remains. (Of course this doesn't do justice to how i

Think of the self as a function, not any particular return value. Stuff comes in, stuff goes out; the self remains. (Of course this doesn't do justice to how inputs transform the self at runtime, but it's just an analogy. If we want to push it further, we could say that the self is a recursive first-class function.)