from Fundamentals of Catholic Dogma
by Ludwig Ott.
1. The highest degree of certainty appertains to the immediately revealed truths. The belief due to them is based on the authority of God Revealing (fides divina), and if the Church, through its teaching, vouches for the fact it a truth is contained in Revelation, one's certainty is then also based on the authority of the Infallible Teaching Authority of the Church (fides catholica). If Truths are defined by a solemn judgment of faith (definition) of the Pope or of a General Council, they are "de fide definita."
2. Catholic truths or Church doctrines, on which the infallible Teaching Authority of the Church has finally decided, are to be accepted with a faith which is based on the sole authority of the Church (fides ecclesiastica). These truths are as infallibly certain as dogmas proper.
3. A Teaching proximate to Faith (sententia fidei proxima) is a doctrine, which is regarded by theologians generally as a truth of Revelation, but which has not yet been finally promulgated as such by the Church.
4. A Teaching pertaining to the Faith, i.e., theologically certain (sententia ad fidem pertinens, i.e., theologice certa) is a doctrine, on which the Teaching Authority of the Church has not yet finally pronounced, but whose truth is guaranteed by its intrinsic connection with the doctrine of revelation (theological conclusions).
5. Common Teaching (sententia communis) is doctrine, which in itself belongs to the field of free opinions, but which is accepted by theologians generally.
6. Theological opinions of lesser grades of certainty are called probable, more probable, well-founded (sententia probabilis, probabilior, bene fundata). Those which are regarded as being in agreement with the consciousness of Faith of the Church are called pious opinions (sententia pia). The least degree of certainty is possessed by the tolerated opinion (opinio tolerata), which is only weakly founded, but which is tolerated by the Church.
With regard to the doctrinal teaching of the Church it must be well noted that not all the assertions of the Teaching Authority of the Church on questions of Faith and morals are infallible and consequently irrevocable. Only those are infallible which emanate from General Councils representing the whole episcopate and the Papal Decisions Ex Cathedra (cf D 1839). The ordinary and usual form of the Papal teaching activity is not infallible. Further, the decisions of the Roman Congregations (Holy Office, Bible Commission) are not infallible.
Nevertheless normally they are to be accepted with an inner assent which is based on the high supernatural authority of the Holy See (assensus internus supernaturalis, assensus religiosus). The so-called "silentium obsequiosum," that is "reverent silence," does not generally suffice. By way of exception, the obligation of inner agreement may cease if a competent expert, after a renewed scientific investigation of all grounds, arrives at the positive conviction that the decision rests on an error.