This was the basic principle in which books in the first Arabian catalogues were classified. There were three divisions.
- Religious Sciences – Koran, theology, law
- Sciences Required to Support Religious Studies – literature, philology, history
- Philosophical Sciences – medicine, astronomy, mathematics
- One containing the most verses of the Koran
- One which cited the most hadith (sayings of the Prophet and his companions)
- One whose author is most esteemed
- One that is the most useful
- One that is most authentic
There was a speific order when several books dealt with the same subject.
- Lerner, Fred. The Story of Libraries. New York: Continuum, 1999.