Abstract
According to the declaration of the First Vatican Council, the ex cathedra teaching of the The Teaching of the Church on Faith and Morals and the Second Vatican Council pope and of the Church's magisterium on the matters of faith and morals is infallible. The difference between the matters of faith and morals has not been explained, but in the matters of morals no infallible document has ever been issued laying claim of being infallible and unchangeable.
On the contrary, the moral teaching of the Church is developing. The Second Vatican Council returned to the matter by introducing the concept of authentic teaching, which is an official teaching of the Church but without the demand of being unchangeable.
All declarations about morality and all moral norms fall into this category. They are bound with the historical, cultural and social situation to the extent that it cannot be maintained that they will be valid forever and under all circumstances in the same way as now if this situation changes.