I'm looking for articles or books that discuss how we account for qualitative identity.
The distinction between qualitative and numerical identity is often drawn, but then the discussion tends to veer solely in favour of numerical.
What I want to know is what are the identity conditions of a book or a theory?
If a small child with no training clearly and cogently explains Pythagorean theorem, what is the nature of the identity statement we are making? On what do we base our judgement that x = y when x and y are concepts, stanzas or chords?
Presumably it is a qualitative identity, x and y share enough of the particular qualities that are required to make our judgement of identity true.
But what are the borderline cases? If the hypothetical monkey-on-a-typewriter were to bash out Romeo and Juliet with every 3rd word as 'Banana', would it still be Romeo and Juliet? If not why not? If so, how many words would have to be replaced to make it not so, and why?
Does anybody have any suggestions for reading material on these topics?