Fr. John Hunwicke offers a very interesting commentary on the post-conciliar disappearance of the Latin breviary:
It is in this context that we must see the requirement of Vatican II (SC 101): “In accordance with the centuries-old tradition [saecularis traditio] of the Latin rite, the Latin language is to be retained by clerics in reciting the Divine Office”. And it is highly significant that it goes on to make any use of the vernacular an exception which bishops can grant only on an individual basis. One might plausibly surmise that this exception may have been envisaged as useful in areas where resources for clerical formation were limited. I wonder how the Council Fathers – or a sizable proportion of them – might have reacted to the information that in less than a decade the bishops of Western Old Europe (whose culture both religiousand secular had been based upon Latin for nearly two millennia, the continent of the great universities in which the civilisation of the Greek and Roman worlds had been transmitted) would regard both this conciliar mandate, and the directions of Optatam totius on seminary training, as an irrelevant dead letter.
Readers of this blog are probably familiar with the other prescriptions of Vatican II for the retention of Latin, and I will not labour the point. I emphasise that I am not basing an argument for the retention of a living Latin culture simply and nakedly upon the words of the Council. The auctoritas for that retention is very much more broadly based, as the Council Fathers themselves emphasised by calling it a saecularis traditio. The concilar mandate is merely an affirmation of the continuity and abiding prescriptiveness of that Tradition; the guarantee that in an age of revolutions the old securities are still in place. Without these words of the Council, it might have been plausibly argued that a radical cultural and intellectual shift had invalidated the previous assumptions. In view of the explicit orders of the Council, such a thesis can only be advanced as a deliberate repudiation of the explicit words of the Council … as well as of the centuries preceding it.