In centuries past, the Church was faced with the important task of recognizing which books belong in the Bible. The Bible itself is not a single book but a collection of many individual books. What the Church sought to establish was what we call the canon of sacred Scripture. The word canon comes from a Greek word that means “standard or measuring rod.” So the canon of sacred Scripture delineates the standard that the Church used in receiving the Word of God. As is often the case, it is the work of heretics that forces the Church to define her doctrines with greater and greater precision.