‘17. On this point there is a difficult problem which needs careful appraisal, since it concerns the faith or the relationship to the Magisterium of many Catholics today even more than in the past. We refer to the fact that in the exercise of its task the ecclesiastical magisterium can fall into error, and indeed has been known to do so. The Church has always been aware of this possibility, has catered for it in her theology, and has developed rules of procedure for such a situation. This possibility of error does not arise with those decisions whose promulgation demands the absolute assent of faith, namely those promulgated by the solemn definition of a Pope or General Council or through the ordinary magisterium.

It is historically incorrect to maintain that subsequently the Church has been found to be in error on such dogmas, though a given dogma is inevitably liable to be understood differently (while preserving its original sense) as it acquires greater precision in the face of past and contemporary misunderstandings.