William D Clinger writes: > Obviously A+A is not equivalent to A in category theory. I don't get this. I don't know anything about category theory, but it seems like "an apple or an apple" is always the same as "an apple". (Whereas "an apple and an apple" is not.) Or are you saying that A = A might not be true? (Don't tell Ayn Rand...) --dougo at place.org