 What is an ability? On one reading, this question is a demand for a theory of ability of the sort described above. On another reading, however, this question simply asks for a rough guide to what sort of things we are speaking of when we speak of ‘abilities’. So understood, this question is not asking for a theory of ability, but for an explanation of what exactly a theory of ability would be a theory of. This section will offer an answer to this question on this second, more modest, reading.