What is Christian Doctrine?

Recently I've been thinking about the doctrine of the Trinity and whether Christian doctrine can develop (as some say) like a seed to a tree, or whether Christian doctrine cannot (or at least has not).

But what exactly is Christian doctrine such that it might be able to develop in the first place?  I am not wondering about the extent of Christian doctrine (e.g. whether subordinationism is a Christian doctrine or a heresy) but what the nature of doctrine is.  What is it to be a doctrine?

What follows are a few undeveloped (very sketchy) thoughts on the matter:

It would seem (at first glance) that it can't consist of sentence tokens or sentence types since Christian doctrine transcends distinct languages (e.g. Christian doctrine might be expressed in Greek or Latin or English but the very same doctrine can be expressed with different sentences).

Perhaps, then, doctrine consists in a proposition or set of propositions.  A view of propositions wherein propositions are thought of as abstract objects would lend itself to thinking that doctrine does not and cannot develop because propositions are not the sorts of things that can change (like the number four, propositions cannot enter into causal relations, ergo they can only change in the Cambridge sense).  Dogma then might be thought of as sentences expressing unchanging doctrine.  Dogma can grow or change as the Church tries to more clearly articulate what the unchanging doctrine is (and always has been).

One odd result, though, of such a view is that there would've been Christian doctrine (Jewish doctrine, etc.) even before there were Christians.  For instance, the proposition that "God exists" or that "Jesus is born of a virgin" were true before there were Christians or even any humans (taking the "is" as atemporal in the latter sentence).  But was there Christian doctrine before there were Christians?  Was their Jewish doctrine before there were Jews?  An affirmative answer strikes me as odd. 

Perhaps, though, we might say that Christian doctrine consists in certain propositions, but those propositions should only be thought of as Christian doctrine when they are expressed in Christian writings (e.g. Scriptures,creeds, and the like).  Nothing about the propositions changes except extrinsically, they're now to be regarded as propositions to be believed by Christians qua Christians.  

Could doctrine develop or change on such a view?  Only if there are some propositions to be believed by Christians at some times but not others.  Could some individual doctrine develop on such a view?  (Again, I'm not asking whether some doctrine has developed but what it might look like if it could).

Maybe.  Let's say the doctrine of the Trinity consists at time t1 of a set of propositions p, q, and r.  At time t2 it consists of propositions p, q, r, s, and t.  At t1 and t2 there is a core set of propositions to be believed but at a later time two additional propositions (in some way intimately related to the other propositions such that we're still dealing with the same doctrine in some sense of "same") are also to be believed.  The doctrine of the Trinity, then, would consist in different sets of propositions at different times.  What then, is the doctrine of the Trinity?  It's that set of propositions to be believed by Christians over the totality of Christianity (I leave aside the epistemological question of how to identify that doctrine versus, say, the doctrine of the Incarnation).

Aquinas offers an alternative view.  In the first question of the Summa and in his commentary on Boethius's De Trinitate (among other places) he understands doctrine as a science and alternatively as a certain sort of wisdom.  Doctrine, then, is something that in its non-derivative or paradigmatic sense inhabits the mind.  What does it mean for the doctrine of the Trinity to be a bit of wisdom and would this have any bearing on the development of doctrine?  I'm not sure and don't have time to think more about Aquinas's view.

A similar view (one which perhaps squares with Aquinas's thoughts) is that doctrine is an interpretation of revelation (revelation construed broadly to include natural revelation); or, perhaps if there is more to doctrine than interpretation, we might think of doctrine as a type of judgment.  (Doctrine couldn't merely be interpretation since presumably Christ promulgated doctrine in revealing things to his apostles but was not himself interpreting that revelation).

This would fit well with a lot of talk in theological circles about doctrine which is implicit in the Scriptures which is rendered more explicit (say) in the Church Fathers.  Judgments are the sorts of things that can have a context and can have an explicit meaning as well as implicit.  Judgments can develop (though they need not).  Judgments can also be expressed in different languages.  Judgments are the sorts of things that can both be revealed by God as well as expressed and promulgated by a Church.

Is there an advantage to the judgment view over the propositional view?