ABSTRACT
It is possible to be able to do something, yet not be able to say exactly what it is that one is able to do. You may, for example, have bicycleriding abilities, but not have mastered the vocabulary that a technical writer would need in order to describe precisely what is being done. The converse is also possible. You may be able to say what is required to be able to do something, without having the ability to do that thing yourself. A skilled golf coach may be able to tell his charge precisely what she needs to do to improve her swing without having that ability himself (BSD I: 31).
