Introduction to the Codex
Within the Greco-Roman world the dominant form of the book was the scroll (or roll). However, the codex was soon born and slowly gathered popularity in its use. Stated simply, the codex was the invention of what we would call the book. This momentous invention marked the shift away from the use of the scroll in ancient society. Technically, all modern books are codices, but generally the term is now reserved for manuscripts which are gathered in the form that we use for books today. While scrolls were made from long sheets of papyrus or parchment stuck together end to end in a long strip, the codex, by contrast, was created by taking a stack of parchment or papyrus leaves, folding them in half and binding them at the spine, with a cover.
Evidence has shown that the basic form of the codex was used as far back as the 3rd century BCE. Remains of wax-coated wooden tablets have been found at the site of the ancient city of Herculaneum, which was all but destroyed with the eruption of Mount Vesuvius in 79 CE. This more primitive form of the codex was replaced by sheets of foldable material which are closer to our modern-day understanding of a book.
It has been suggested that it was Christianity which ensured a rise in the use of codices. Its use certainly has a connection with Christianity, though debate still continues as to exactly why this is. Currently there is a large body of academic interest over specific questions such as who exactly invented the codex and why it specifically came into use. It appeared that Christianity much preferred the use of the codex in comparison to that of the scroll, and for wide ranging reasons. John Barton has suggested that it was because Christians wanted to distance themselves from Judaism, while other suggestions include its greater efficiency in terms of price and physical space to write on.
Various manuscript discoveries - such as the Papyrus Egerton 2 (apocryphal gospel) - suggest that the codex was the widely established Christian practice certainly by the early 2nd century CE, if not by the late 1st century CE. During times of Christian oppression and persecution, codices were often hidden; archeological records have found codex collections buried in sealed ceramic jars.
Yet the books found at Nag Hammadi indicate that the codex was not a medium of literature exclusive to Christians. Nevertheless, it was not until the 4th century CE that the codex was preferred over the roll by the broader Greco-Roman and ancient society. Some have suggested that the declaration of Christianity as the official state religion is responsible for this widespread shift.
A single-quire (i.e. a single collection of sheets) codex could hold a maximum of around 250 pages (around 125 leaves), and allowed various benefits such as easy access, efficiency (due to the writing being on both sides), and low cost. Since early Christian missionaries were rarely wealthy, this last advantage was particularly favourable. There is also evidence given by the scholar T.C. Skeat (e.g. The Birth of the Codex, with Colin H. Roberts) of multiple-quire codices which are made up of numerous quires, all bound at the spine. Early examples of these include the 4 Gospels and the book of Acts. Equally noteworthy is the use of private miniature codices in the early 2nd century which were around 10cm wide. Larry Hurtado has supported the claim that the codex was particularly favoured by Christians - he noted that it played a large role in the development of the corpus of the New Testament Canon. J.K. Elliott wrote that “canon and codex go hand in hand in the sense that the adoption of a fixed canon could be more easily controlled and promulgated when the codex was the means of gathering together originally separate compositions” ('Manuscripts, the Codex & the Canon, JSNT 63, 1996).
The emerging Christian movement, much like the Jewish religion, would therefore be defined and shaped by the production and use of books, all of which stemmed from this influential shift from scroll to codex.
For further information see:
Frost, Gary. “Adoption of the Codex: Parable of a New Reading Mode.”The Book and Paper Group Annual. 1998. http://cool.conservation-us.org/coolaic/sg/bpg/annual/v17/bp17-10.html.
Resnick, Irvin. ‘The Codex in early Jewish and Christian Communities’, The Journal of Religious History 17 (1992): 1-17. Accessed 17 March 2016. http://onlinelibrary.wiley.com.ezproxy.is.ed.ac.uk/doi/10.1111/j.1467-9809.1992.tb00699.x/epdf
For some implications of the growing use of the codex in the ancient world see - http://wol.jw.org/en/wol/d/r1/lp-e/2007404#h=5
For some possible further causes as to why Christianity adopted the use of the codex see -