Why did the Catholic Church decide to have a Bible? As far as I know, the Catholic Church considers God's revealed truth in Sacred Scripture to be part of, but by no means the sum total of Divine Revelation.  Sacred Scripture is the written part of our Traditions, but it is entirely possible to have a Catholic Church without Biblical literacy (or literacy at all).

So, why did the Church decide on having a canon of scripture in the first place?  Did the Church Fathers (Augustine and prior) consider that having a set of writings that resides somehow outside the authority of the Church would eventually cause fractures due to private interpretation?  Or was it necessary to prevent further errors owing confusion coming from  the existence of the many gnostic and apocryphal later writings?
Why a canon?

Why not a potato gun?
Even before John died in Patmos there started to be other books which claimed to come from the Apostles or otherwise claimed to have been inspired by God. While in some cases this was not a terrible thing (some of them are quite dull, actually) others of these were wild departures from the teachings of Christ and were arguably destructive to the soul. As a response the Church started to gather together lists of what documents were known to have been of Apostolic origin. I believe the first such (or the first that we know about) list dates back to the end of the second century. It actually took the better part of three centuries for a genuine consensus to exist and when it was finally agreed upon that was more-or-less a gentleman's agreement: no ecumenical council decided the fact, everyone simply agreed.

It was over a millennium later that someone presented a serious challenge to the canon. One of the less talked about points which was a bi-product of the reformation was the fact that people started to call into question which books actually belonged in the Bible and which did not. In a response to this, the Council of Trent officially (and bindingly) defined the canon.

What benefit is there to a canon?

Among others:


What benefit is there to have a creed? What benefit is there in having a Catechism? One of the chief benefits of a canon is that it functions as a point of reference. You can deny Augustine, but you can't deny Paul.
It also served liturgical purposes. Even from the road to Emmaus, the Church has associated the breaking of the bread with the reading of scripture. Setting a defined list of scripture guarantees that what is read is something worth reading.




You may want to check out this article on the process.