Of course I believe Jesus kept His promise.No you don't. Not really. The traditionalists who have returned to union with Rome believe in Him. But not you. You believe in Klaus Gamber.
--ultima ratio
Please consider the following:
And I make a distinction you don't seem to appreciate, but which any theologian understands who is worth his salt: not everything a council says is guaranteed Divine Protection. Only those pronouncements which are specifically declared dogmatic are binding on the faithful.
--ultima ratio
Pius XII refers to a declaration on the inerrancy of scripture from Vatican I as a "solemn definition of Catholic doctrine," although in the Vatican I document it wasn't a canon in the form: If someone shall say . . . . let him be anathema. Not only can statements such as this from a Church Council be binding, papal encyclicals can be binding as well:
These books the church holds to be sacred and canonical not because she subsequently approved them by her authority after they had been composed by unaided human skill, nor simply because they contain revelation without error, but because, being written under the inspiration of the Holy Spirit, they have God as their author, and were as such committed to the church.
--Vatican Council I
In our own time the Vatican Council, with the object of condemning false doctrines regarding inspiration, declared that these same books were to be regarded by the Church as sacred and canonical "not because, having been composed by human industry, they were afterwards approved by her authority, nor merely because they contain revelation without error, but because, having been written under the inspiration of the Holy Spirit, they have God for their author, and as such were handed down to the Church herself."When, subsequently, some Catholic writers, in spite of this solemn definition of Catholic doctrine, by which such divine authority is claimed for the "entire books with all their parts" as to secure freedom from any error whatsoever, ventured to restrict the truth of Sacred Scripture solely to matters of faith and morals ...
--Pius XII, Divino Afflante Spiritu, Sep. 30th, 1943
Now that we have shown that the binding nature of Church Councils isn't quite as narrow as you think, and have shown that even papal encyclicals can be binding, here is another Pre-Vatican II source on the authority of Church Councils:
Nor must it be thought that the things contained in Encyclical Letters do not of themselves require assent on the plea that in them the Pontiffs do not exercise the supreme power of their Magisterium. For these things are taught with the ordinary Magisterium, about which it is also true to say, 'He who hears you, hears me.' [Lk 10. 16]. . . If the Supreme Pontiffs, in their acta expressly pass judgment on a matter debated until then, it is obvious to all that the matter, according to the mind and will of the same Pontiffs, cannot be considered any longer a question open for discussion among theologians.
--Pius XII, Humani Generis, Aug. 12th, 1950
Proof From Tradition
If, during the early centuries, there was no explicit and formal discussion regarding ecclesiastical infallibility as such, yet the Church, in her corporate capacity, after the example of the Apostles at Jerusalem , always acted on the assumption that she was infallible in doctrinal matters and all the great orthodox teachers believed that she was so. Those who presumed, on whatever grounds, to contradict the Church's teaching were treated as representatives of Antichrist, and were excommunicated and anathematized.It is needless to go on multiplying citations, since the broad fact is indisputable that in the ante-Nicene, no less than in the post-Nicene, period all orthodox Christians attributed to the corporate voice of the Church, speaking through the body of bishops in union with their head and centre, all the fullness of doctrinal authority which the Apostles themselves had possessed; and to question the infallibility of that authority would have been considered equivalent to questioning God's veracity and fidelity.
- It is clear from the letters of St. Ignatius of Antioch how intolerant he was of error, and how firmly convinced that the episcopal body was the Divinely ordained and Divinely guided organ of truth; nor can any student of early Christian literature deny that, where Divine guidance is claimed in doctrinal matters, infallibility is implied.
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Ecumenical Councils
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That an ecumenical council [ that is convened with the approval of the Pope ] is an organ of infallibility will not be denied by anyone who admits that the Church is endowed with infallible doctrinal authority. How, if not through such an organ, could infallible authority effectively express itself, unless indeed through the pope? If Christ promised to be present with even two or three of His disciples gathered together in His name (Matthew 18:20), a fortiori He will be present efficaciously in a representative assembly of His authorized teachers; and the Paraclete whom He promised will be present, so that whatever the council defines may be prefaced with the Apostolic formula, "it has seemed good to the Holy Ghost and to us." And this is the view which the councils held regarding their own authority and upon which the defender of orthodoxy insisted. The councils insisted on their definitions being accepted under pain of anathema , while St. Athanasius, for example, says that "the word of the Lord pronounced by the ecumenical synod of Nicaea stands for ever" (Ep. ad Afros, n. 2) and St. Leo the Great proves the unchangeable character of definitive conciliar teaching on the ground that God has irrevocably confirmed its truth ...
Infallibility, Catholic Encyclopedia, 1910