I conceive then that the Depositum is in such sense committed to the Church or to the Pope, that when the Pope sits in St. Peter’s chair, or when a Council of Fathers & doctors is collected round him, it is capable of being presented to their minds with that fullness and exactness, under the operation of supernatural grace, (so far forth and in such portion of it as the occasion requires,) with which it habitually, not occasionally, resided in the minds of the Apostles;—a vision of it, not logical, and therefore consistent with errors of reasoning & of fact in the enunciation, after the manner of an intuition or an instinct. Nor do those enunciations become logical, because theologians afterwards can reduce them to their relations to other doctrines, or give them a position in the general system of theology. To such theologians they appear as deductions from the creed or formularized deposit, but in truth they are original parts of it, communicated per modus unius to the Apostles’ minds & brought to light to the minds of the Fathers of the Council, under the temporary illumination of Divine Grace.
That's an important clue to legitimate development of doctrine. While later developments that become irreformable, by means of dogmatic definition or ordinary teaching, are not usually strict logical deductions from earlier formulations, they do make explicit what may only have been implicit in the minds of the Apostles. When some Christians—such as Orthodox apologists and fundamentalist Protestants—deny development of doctrine, they are concerned to rule out any alteration, by innovative addition or by mere negation, to the deposit of faith. That concern is justified. It is also allayed by Newman's general approach.
Yet I'm amazed by how often the point is missed. In a comment within a Pontifications thread that is now closed, Perry Robinson criticizes my adaptation of that approach thus:
There seems to be a rather significant difference between reasonably seeing [Vatican I] in the past data as implicit, AND that “Orthodox doctrine fails to recognize the full implications of what both sides believed for nearly a thousand years.” I don’t see how one gets from the former to the latter. Sure it may be reasonable to see the data that way, but that doesn’t amount to an IMPLICATION. A “likely story” isn’t the same as a proof.I'm afraid that's just not how things are, or were.
When you can find something like Newman’s Essay on the Development of Doctrine, among the Orthodox, your argument might have traction, for the Orthodox do not object primarily on the grounds that such data icannot be read as being implicit in past texts, but rather that there is no development of doctrine in the first place. If God is not being, and there are no relations of being in God, then dialectic has NO place in theology. Therefore, employing the dialectic of reason to “discover” implicit teachings that become manifest later, that is the very idea of development, is simply out of bounds. The fact that on your gloss Ratzinger admits that the past sources do not pick out V1 is sufficient proof that it is not apostolic. If it were, it wouldn’t require “development.”
As for Innovation, well the filioque is a prime example. Rome opposed it for centuries while it “developed” under its condemnation, until Rome could withstand no longer.
When Newman and Ratzinger affirm that Vatican I's doctrine of papal primacy is implicit in the earlier data, they are not claiming that the former can be got from the latter by logical deduction, which is what Robinson's criticism presupposes. "Proof" in the logical sense is accordingly not available in this matter, or indeed on matters of revealed truth generally. From the standpoint of reason alone, the best one can get is indeed a "likely story." The question, as always, is whose story to accept. That is a question of which authority to accept, which is itself a matter of faith. Thus reason is always relevant to such matters but is never in itself dispositive. Its role is primarily negative: to rule out what is self-contradictory.
Presumably as a way of indicating that I beg the question, Robinson repeats the formula that "for the Orthodox...there is no development of doctrine in the first place." But that won't do either. For one thing, I doubt that that's an irreformable stance of the Orthodox communion itself, as distinct from the polemical stance of many Orthodox apologists. Nor should it be, for of course doctrine has developed; the question is not whether it has done so, but how it can legitimately do so. Newman gave an account of that, which is much appreciated by the present pope. Robinson tries to absolve himself of the need to do so by denying the fact to be accounted for. That doesn't so much engage the question as march on the spot.
Of course he's got what appears to be another argument: If God is not being, and there are no relations of being in God, then dialectic has NO place in theology. Therefore, employing the dialectic of reason to “discover” implicit teachings that become manifest later, that is the very idea of development, is simply out of bounds. Now for one thing, and try as I may, I've never been able to make sense of the claim that 'God is not being'. I can make sense of the claim that God is not one being among others, to be subsumed under categories such as Aristotle's; I can make sense of the claim that God's being is incomprehensible, in the sense that it's infinitely beyond what we can say about it. Both those claims are true and taken as a matter of course by Catholic theologians. But even Orthodoxy affirms that the Father is the cause of the existence of the Son and the Holy Spirit, which would not make sense if Robinson's claim were taken at face value. I don't know how to take that claim save in senses that I've just noted are shared by Catholics. Hence, his cryptic remark in passing about "dialectic" is neither here nor there, and thus provides no argument against development.
As for the filioque, it simply isn't true that "Rome opposed it for centuries." What Rome opposed for centuries was interpolating it into the Nicene-Constantinopolitan Creed. And for good reason: the clause did not express a point of faith that the East could recognize as her own. That's why Rome should never have introduced it into the Creed. But that's a primarily pastoral concern that can be addressed without altering the doctrinal landscape.