How can a holy book be justification for its own authority?
This is a genuine question.
If someone actually knows a
logical answer to this, even if it requires belief in the supernatural, that's fine. My understand (because I was told this by theists) used to be that God confirms to theists, through some kind of spiritual communication, that the Bible/Qur'an is in actual fact, his book, thus giving it authority.
Naturally I don't believe God speaks to people in their own head, but that did at least make sense as an argument, in the same way that Mick Jagger saying "This biography of me is al'ight" would give authority to a biography of Mick Jagger, even if someone believes Mick Jagger is actually a robot.
Because of that understanding of divine communication I thought we were all well passed the argument that faith in the Bible is cyclical, and based on this (apparently false) understand I had I used to defend theists against charges that their faith in the Bible was cyclical, a charge that I saw as the result of lack of understanding of atheists. Oh how foolish I feel now

So anyone, believers or not believers, explain this?