The question of development of Doctrine is one that vexes many non-Catholics, and not a few Catholics as well. The argument can well be made that Doctrine is set by this quote from CCC #65:
Christ, the Son of God made man, is the Father’s one, perfect, and unsurpassable Word. In him he has said everything; there will be no other word than this one.
Indeed, one could even argue a form of Sola Scriptura if that quote were to be taken out of context. Fortunately as Catholics we believe context is key, and the very next paragraph in the Catechism clarifies this very critical point:
Yet even if Revelation is already complete, it has not been made completely explicit; it remains for Christian faith gradually to grasp its full significance over the course of the centuries. (CCC #66)
This concept is covered masterfully by Blessed John Henry Cardinal Newman in his Essay on the Development of Doctrine. It is not, as you could well guess given the complexity of the topic, a short work but it is none the less one that ought to be high on the to-be-read list for every Catholic and in particular every Catholic catechist.
