A personal way to govern: Why Pope Francis uses Apostolic Letters the way he does

It is no coincidence that Pope Francis chose the form of an apostolic letter to write about liturgy. Nor that he chose to write it one year after the publication of the Traditionis custodes, the motu proprio with which he abolished the liberalization of the Traditional Latin Mass by Benedict XVI.

Published on June 29 and entitled Desiderio desideravi, the document not only drives home his concerns with the liturgy. It also shines a light on the thought — and the modus operandi — of Pope Francis.

In the 15-page apostolic letter, the pope said he wanted “to invite the whole Church to rediscover, to safeguard, and to live the truth and power of the Christian celebration.”

Pope Francis also said, after writing a letter to bishops to accompany Traditionis custodes, he wished to address all Catholics with some reflections on liturgical formation, the theological importance of the Mass, and acceptance of the liturgical documents of the Second Vatican Council.

Notably, this is the 83rd time that Pope Francis has used the form of the apostolic letter to convey an authoritative opinion.

When it comes to expressing the pope’s teaching authority, his magisterium, an apostolic letter ranks fourth in the hierarchy of pontifical documents. The most important would be an apostolic constitution, followed by a papal encyclical, and then an apostolic exhortation.

Pope Francis, however, has always favored "light" legislative instruments, which require less effort in drafting – and do not undergo a longer approval process.

An apostolic constitution, for example, must be consistent with canon law and other prescriptions of the Church. For this reason, Praedicate evangelium, which regulates the functions and offices of the Curia, has had a long gestation period and still awaits full implementation.

The same is true of a papal encyclical, which is concerned with expressing the magisterium – and cannot be linked only to contingent moments.

The third most important kind of document, an apostolic exhortation, is a more particular and personal instrument of the pope. In the case of a post-synodal exhortation, it will draw on the fruits of a Synod of Bishops.

It is worth noting that Pope Francis' governmental program takes the form of an apostolic exhortation: Evangelii gaudium replaced the post-synodal apostolic exhortation expected after the Synod on the Word of God in 2012.

Of that synod — the last of the pontificate of Benedict XVI — no trace remains.

When Pope Francis had to legislate, he mainly used the form of a motu proprio (the Vatican website lists 49 of them) and rescripts. These are officially called rescripta ex audientia sanctissimi, i. e. orders of the Pope, written following a personal audience.