[quote=mosher]To over simplify the issue you can think of it as a hierarchy with Dogma at the top and tradition at the bottom and Doctrine in the middle.
Doctrine are those things that we know to be true but at the same time we can gain deeper insights. An example is the doctrine of “extra ecclesia non solus” which is properly translated as “apart from the Church there is no salvation.” Since the Second Vatican Council there has been an apparent change in this doctrine. In fact there is no change, however it is understood a little different then it was in the past. We still belive the doctrine but there has been a small development in out understanding of the doctrine.
Peace be with you!
What mosher just said is exactly right. And the salvation doctrine is a excellent example to use to explain the development of doctrine. I would go a little further to explain this apparent change. Before, it was understood to mean that one must belong to the Catholic Church (note the uppercase C). Now it is understood to mean part of the catholic Church, using the true meaning of the word catholic as universal. Even non-Christians can be saved according to this understanding because while their religions do not contain the fullness of the Truth, they do contain pieces or parts of that Truth.