In theory, an Ecumenical Council can teach either/both infallibly or non-infallibly. And a non-infallible teaching can err, though not gravely. But I’ve never found any error of any type in any Ecumenical Council’s teaching. Perhaps Ecumenical Councils are infallible in all that they teach.
As for Vatican II, in all the many years of study of those documents, I’ve never seen any error at all, no matter how small, in any teaching of that Council. And when has any Council or Pope ever corrected a non-infallible teaching of a past Council?
I suggest that perhaps all Ecumenical Councils are inerrant in all that they teach as a truth of Tradition, Scripture, Magisterium.
So many times, when people claim that Vatican II erred, they simply compare their own understanding to that of the Council and assume that the Council errs whenever the two disagree. Essentially, the critics of Vatican II assume that their own mind is infallible. They don’t say that. But it is an assumption in their every argument against a Pope or a Council.
My faith tells me to accept everything that the Second Vatican Council teaches on faith, morals, and salvation. I don’t put my reason above the Council to continually judge its every teaching. I have faith in the teachings of Christ in that Council. And the result is peace, holiness, faithfulness to God and faithfulness to each and every Pope.
I stand on faith, not on my own fallen reason.
by
Ronald L. Conte Jr.
Roman Catholic theologian and translator of the Catholic Public Domain Version of the Bible.
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the reproach of Christ 
Dear Ron,
Thank you for this article. I agree with what you say about Vatican II.
St. Robert Bellarmine, at the end of De conciliis, Liber II, chapter IX says “we hold by Catholic faith that legitmate councils confirmed by the Supreme Pontiff cannot err” (ex fide Catholica habeamus concilia legitima a Summo Pontifice confirmata non posse errare).
Bellarmine here is speaking of matters of faith and morals. Some teachings of ecumenical councils, especially on matters of discipline, have been superseded, let go, or revised. Rather than speak of such teachings as errors, I believe it’s more accurate to say these were teachings that were not per se irreformable. Some theologians believe that if teachings are not per se infallible, they are, therefore, liable to error. I would rather speak of them as non-irreformable, which is the way the Congregation for the Doctrine of the Faith speaks of them in numbers 24 and 28 of its 1990 instruction, Donum Veritatis.
It’s possible that ecumenical councils can make judgments on contingent or historical matters that are subject to qualification or correction. For example, Fr. Ludwig Ott, in Fundamentals of Catholic Dogma (Baronius Press, 2018, p. 162) states that the Sixth General Council” (Constantinople III) “wrongly condemned [Honorius I] as a heretic.” As you know, Ott then notes that, when Pope Leo II (682-683) confirmed the condemnation of Honorius I, he did so because of Honorius’ negligence rather than heresy. Ecumencial councils can teach infallibly on matters of faith and morals. Whether Honorius I actually held to the Monothelite heresy is a matter of history not faith and morals.
I hold to the position of Bellarmine. Legitimate ecumenical councils confirmed by the Roman Pontiff cannot err in matters of faith and morals. They can, however, make judgments on discipline, history, or open theological questions that are not per se irreformable. In other words, they are subject to revision or qualification. To speak of such judgments as “errors” is not, in my view, accurate.
Robert, Thanks. I agree that the inerrancy of Councils is limited to faith and morals.I can’t think of any Conciliar error on faith or morals, so I think Bellarmine is right. The interesting result of this inerrancy, though, is that the teachings of Vatican II on faith and morals would then be infallible. This further undermines the position of the Francis critics.