Infallibility 101: Sometimes Only A Single Sentence In A Document Is Infallible

Identifying Infallible Teachings

Sometimes people ask, “Is this document infallible?”

The question is problematic because the Magisterium doesn’t issue documents whose teaching is infallible from beginning to end. Instead, it issues documents that contain individual propositions that are infallible.

In Ineffabilis Deus (1854) and Munificentissimus Deus (1950)—the documents that defined the Immaculate Conception and Assumption of Mary—only a single sentence in each document was infallible (i.e., the definitions themselves).

The rest of the documents provided context for the definitions.

A better question would be, “Is this teaching infallible?”

The initial presumption is that it’s not: “No doctrine is understood as defined infallibly unless this is manifestly evident” (CIC 749 §3).

Note the forcefulness of the language: It mustn’t just be evident that a doctrine is infallible; it must be manifestly (clearly) evident. This places a weighty burden of proof on one wishing to claim that a teaching is infallible.

Neglect of this principle is a frequent source of problems. Many people casually assume a prior teaching is infallible and then encounter difficulties squaring it with a more recent one.

But the Church has always been careful about what it defines, and the rule has always been that a teaching is not to be regarded as infallible unless the contrary is clear.

So what factors overcome the presumption of non-infallibility?

This depends on how the Magisterium teaches it.

Vatican II provided what is currently the most doctrinally developed and authoritative explanation of the conditions in which the ordinary and universal magisterium teaches infallibly:

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 (Lumen Gentium, 25; cf. CIC 749 §2).

Vatican II thus indicates the following criteria must be met for the ordinary and universal magisterium to define a teaching:

1. The bishops of the world maintain communion among themselves.
2. They maintain communion with the successor of Peter.
3. They teach authentically (i.e., authoritatively).
4. They teach on a matter of faith and morals.
5. They are in agreement on one position as definitively to be held.

The first two conditions require that the bishops not be in a state of schism, which is “the refusal of submission to the supreme pontiff or of communion with the members of the Church subject to him” (CIC 751).

The third condition requires that they must teach on a matter authoritatively. It wouldn’t be enough for them to privately believe an opinion among themselves. It must be communicated to the faithful as an authoritative teaching.

The fourth condition requires the matter to concern “faith and morals.” That is, it must either be a revealed truth or one required to properly guard and explain revealed truth (§§428-450). Bear in mind that “morals” (Latin, mores) includes aspects of Christian life that go beyond the principles of moral theology (§429).

The final condition requires three specific things:

a) It requires the bishops be in agreement. This is generally understood as a moral unanimity among them. It wouldn’t be enough if only a portion or even a mere majority were in agreement, but it needn’t be every single bishop in the world.

b) The bishops must agree on one position. It isn’t enough if they consider a range of positions legitimate. They must agree on a single, specific truth.

c) They must agree this truth is “definitively to be held” by the faithful, thereby bringing all legitimate discussion to an end. If the bishops merely agreed that it should be held then the teaching would be authoritative but non-infallible. It is only when they agree a teaching is absolutely mandatory that infallibility is engaged.

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