There is an amusing video on YouTube showing an American Latinist engaging priests in the Vatican in spoken Latin. He remarks that he spoke to a dozen priests, but only three were brave enough to go on camera with him and use Latin in actual dialogue.
Spoken Latin might sound like the preserve of hobbyists, like spoken Elvish or Klingon, but being able to speak a language is the ultimate test of fluency, and for the Church, Latin isn’t just any other language. As well as being the sacred language of the liturgy, it is an indispensable key to the Church’s theology, history, law, philosophy, and poetry. As Pope Benedict XVI described it, it is the language the Church considers as her own.
It is for this reason that Latin has always formed an essential part of the education of the clergy. The Second Vatican Council’s decree on Priestly Training, Optatam Totius, says seminarians “are to acquire a knowledge of Latin which will enable them to understand and make use of the sources of so many sciences and of the documents of the Church” (13). This means a serious grasp of the language: being able to sit down and read St. Augustine, for example—not as a homework exercise, but because you want to know what he says about something.
It is quite an irony that some in the Church who like to align themselves with Vatican II, in contrast to the practice of the Church before the Council, seem less comfortable with something that has been entirely consistent before, during, and after it: the importance of Latin in the education of future priests.
In very year of the opening of the Council, Pope St. John XXIII reaffirmed the importance of Latin for seminarians in his apostolic constitution Veterum Sapientia. Pope St. Paul VI kept up the pressure with a whole series of documents, including the 1970 Ratio fundamentalis on seminary education. The revised versions of this document said the same thing, in 1980 under Pope St. John Paul II and in 2016 under Pope Francis . It is also reiterated in the 1983 Code of Canon Law (Canon 249).
One does not need to argue about hermeneutics of reform or of rupture in relation to these documents. They are consistent, repeating over and over again what had been said before the Council: that priests should be comfortable reading Latin, not just for the liturgy (for which a more basic Latin education would be sufficient), but for their studies. These documents do reveal a little weariness: their authors were conscious that their instructions were not being universally obeyed. But if one wishes to know what the Church desires, there can be no ambiguity about it. (More about these documents can be read here.)
Why is Latin regarded as so important? The documents often refer to the Fathers of the Church, but the use of Latin for important documents has continued up to the present day. Not all of this material has been translated, and even when it has been, to read a translation is always second best. You can’t fully engage with a thinker or an artist if there is a translator standing between you.
The problem is more serious still when one considers the Church’s universal nature. To make a document available in the vernacular for the Church around the world, it is not enough for it to exist in Italian. Italian is only the world’s thirteenth most widely spoken language. Few people learn it as second language at school. It is perfectly natural for the Roman Curia to use a lot of Italian, but this language is not well suited to getting a message across to the world’s two billion Catholics. English might seem the obvious alternative, but while it dominates the worlds of business and popular culture, it has much less weight in the Church, where Spanish is more widely spoken, more important modern theological texts have been composed in German, and major regions can be reached only in French or Portuguese. This raises the question: just how many languages does a cleric engaged in the Church’s international debates and administration need to know?
The days when every educated person, including every priest, knew Latin were simple by comparison. That made possible communication not only with the past, but with people in the present. When the Fathers of Vatican II gathered, it was possible for them to use Latin as a medium for the exchange of ideas. In the Synods of Bishops that have taken place in recent decades, bishops have found themselves able to communicate directly only with people from their own language groups. The proposals of each language group have to be translated into Italian, and back out into all the other languages, to be considered by others. It is a process more reminiscent of the Tower of Babel than Pentecost.
Moreover, not only does the need for multiple translations slow down the exchange of thoughts and inevitably introduce inaccuracies, but it gives immense power to the translators, whether they exercise this power deliberately or not. Studying the Church’s documents with an eye to the different language versions reveals systematic biases, though not always in the same direction. When documents composed in a vernacular language are put into Latin, they are often tightened up—made more theologically precise and, often, conservative. A famous example of this was definition of lying in the Catechism of the Catholic Church: editions based on the original French had to be corrected by reference to the Latin into which the French was translated, because although the Latin was later in time, it was the official version.
On the other hand, when Latin documents are turned into English, they are often made to appear more liberal. The liturgy is one well trodden example; the documents of Vatican II have been another battleground for translators. A endemic problem with the latter was the use of the English word reform, often used to translate Latin words such as instauratio, which means not “reform,” but “restore.” In this complexity, those without Latin are at a severe disadvantage.
As the video mentioned above makes clear, it is still possible to communicate in Latin; it just requires an effort. English-speaking Catholics without Latin should reflect that they have many co-religionists with whom they have no common language, including many untranslated thinkers of the past. Just as C.S. Lewis was able to carry on a correspondence in Latin with the Italian priest, later canonized, Don Giovanni Calabria, so we open up enormous possibilities of communication by improving our Latin. This is an obligation particularly incumbent on priests.
In the words of Pope St. John Paul II on Latin, the Church has “always reckoned it to be a bond of unity, a visible sign of stability, and an instrument of mutual friendship” .
 Cf. Apostolic constitution Veritatis Gaudium (2018) 36.3, 66.1b.
 Pope St. John Paul II, Allocution to the winners of the 12th Vatican competition, 22 November 1978.