Q&A 3, Second Answer

The basic form of my question is: Is writing which is untrue, but which the writer believed to be true, fiction or nonfiction?

I am not sure, but I think I would call such writing nonfictional.  I think that writing which is untrue and intended to be believed is deception or lying, writing which is untrue and intended to be disbelieved is fiction, and writing which is untrue, but intended to be true, is nonfictional (and the product of a mistaken author).  Unless the intent for a work to be fictional is there, I do not think the work can be fiction.