There are three types of infallibility of the Magisterium:
A. Papal Infallibility – solemn definitions of the Pope
B. Conciliar Infallibility – solemn definition of the body of Bishops gathered with the Pope at an Ecumenical Council
C. Ordinary and universal Magisterium – definitive teachings without a particular solemn definition when the body of Bishops are dispersed in the world, but in communion with and led by the Pope.
Lumen Gentium 25: “Although the individual bishops do not enjoy the prerogative of infallibility, they nevertheless proclaim Christ’s doctrine infallibly whenever, even though dispersed through the world, but still maintaining the bond of communion among themselves and with the successor of Peter, and authentically teaching matters of faith and morals, they are in agreement on one position as definitively to be held. This is even more clearly verified when, gathered together in an ecumenical council, they are teachers and judges of faith and morals for the universal Church, whose definitions must be adhered to with the submission of faith.”
Now here is the insight, in three parts.
First, the Pope could possibly exercise Papal Infallibility while at an Ecumenical Council. Suppose that there is a particular controversy during an Ecumenical Council. The bishops cannot come to an agreement. So the Pope decides to issue a decision on the matter under Papal Infallibility, during the Council. That decision is not of the Ecumenical Council, as the bishops could not agree. It is of papal authority alone. Then, subsequently, the bishops must assent with the full assent of faith to the infallible teaching. And the Council then continues.
Second, Conciliar Infallibility does not occur only at an Ecumenical Council. This is controversial and speculative; I could be wrong and I am willing to accept correction from the Magisterium. But I believe that the Pope can gather with the bishops dispersed in the world via communication, and then they can issue a solemn definition which would fall under Conciliar Infallibility, rather than the ordinary and universal Magisterium, because it would be a particular solemn definition. The teachings of the ordinary and universal Magisterium are definitive without a particular definition.
This has happened, in the case of Evangelium Vitae. Pope Saint John Paul II states that he consulted a gathering of Cardinals. Then subsequently every diocese in the world was consulted, and the result was three solemn definitions on morals, condemning murder, direct abortion, and euthanasia. I believe these definitions fall under Conciliar Infallibility, as the mode of infallibility of the Magisterium.
Thirdly, and this is most important, during an Ecumenical Council, when the Pope and the body of Bishops teach definitively on matters of faith and morals, a teaching binding on the whole Church, they exercise the ordinary and universal Magisterium. In this way, all the definitive teachings of every Council are infallible, those that are solemn definitions and those that lack a solemn definition but are nonetheless definitively taught (e.g. Lumen Gentium 25).
Otherwise, an Ecumenical Council might discuss a topic and decide to leave it open to further theological inquiry, and so, without a definitive teaching, the Councils mere comments on the topic would not be dogma. But I don’t think any errors would occur in any case.
For the body of Bishops and the Pope do not lose their ability to teach under the ordinary and universal Magisterium when gathered together in a Council. And neither do they lose their ability to issue solemn definitions when they are dispersed throughout the world. But what if some circumstance were to prevent the bishops from gathering in a Council. Would this circumstance thereby deprive the Church of one of the three modes of infallibility of the Magisterium? Not at all. God does not permit the Church to lose Her gifts.
The fact that the Bishops are gathered, or are dispersed in the world, is not a condition for infallibility. And therefore the type of infallibility where they are gathered, can be exercised when they are dispersed; and the type of infallibility where they are dispersed, can be exercised when they are gathered.
Furthermore, even when not issuing a definitive decision, I believe that there are no grave errors possible in what a Council decides under discipline, as the Pope gathered with the body of Bishops has the fullness of the gifts and authority of Christ.
It remains a matter to be definitively determined by the Magisterium, whether an Ecumenical Council ever teaches non-infallibly and therefore with protection from every grave error, but not from lesser errors. I believe no errors are possible. I have not seen any convincing arguments that any TEACHING of any Council was ever in error. One might criticize decisions on discipline, but these are certainly protected at least from all grave error.
Ronald L. Conte Jr.