Why is relative identity an unpopular theory? What I read generally asserts that

Why is relative identity an unpopular theory? What I read generally asserts that it is not accepted by very many philosophers, but some of the examples don't seem defective at first blush, like two copies of Animal Farm being identical stories but distinct books. What don't philosophers seem to like about the theory of relative identity?

Read another response by Stephen Maitzen
Read another response about Identity