There is a five-word principle the Church has lived by since at least the fifth century: lex orandi, lex credendi. The law of prayer is the law of belief. How we pray is what we believe. Change the words we pray with, and over time you will change what we believe.

This article is about what that principle has to do with Latin — and why a 21st-century Catholic, in a world where the vernacular Mass is the norm, should still care.

Where the phrase comes from

The full Latin tag is legem credendi lex statuat supplicandi — "let the law of supplicating establish the law of believing." It belongs to a fifth-century monk named Prosper of Aquitaine, a disciple of St. Augustine, who used it to settle an argument about grace. The Pelagians wanted to argue that grace was a kind of optional accelerant on top of human effort. Prosper pointed out that the Church, in her oldest liturgical prayers, asks God for the conversion of unbelievers, for the perseverance of saints, for the grace to do every good work. If that is how the Church prays — and it is — then grace must be everywhere prior and prevenient. The lex orandi proved the lex credendi.

The same logic has been used by the Church on every major doctrinal question ever since. The early Christians prayed to Mary; therefore she is to be honored. The faithful prayed for the dead; therefore there is a purgation after death. The Eucharistic Prayer addressed Christ as God; therefore Christ is God. The Church does not invent doctrine and then teach the faithful to pray accordingly. She prays the faith first, and articulates it later.

This is why Pope Pius XII could write in his 1947 encyclical Mediator Dei: "The entire liturgy ... has the Catholic faith for its content, inasmuch as it bears public witness to the faith of the Church." The liturgy is not a vehicle for the faith. The liturgy is the faith, prayed.

What this has to do with Latin

Here is where the principle gets concrete. The Roman Rite — the Mass and Office that have been celebrated in the Latin-speaking West for at least 1,600 years — prays in Latin. Not because Latin is sacred in the way Hebrew was sacred to the Temple, but because the Church's actual liturgy, the corpus of texts in which her faith is enshrined, was composed and prayed in Latin for nearly two millennia. The words of the Roman Canon, the antiphons of the Office, the chants of the Holy Week liturgies — these are Latin texts. They were written in Latin, composed for Latin, sung in Latin, prayed in Latin by every Western Christian from the time of Pope Damasus I (4th c.) to the time of Paul VI.

If lex orandi, lex credendi, then those Latin words are not just a vehicle the Church used to use. They are part of the deposit. They are what the Church has prayed. They carry, in their grammar and word-choice and sound, sixteen centuries of theological precision that any translation — by definition — loses something of.

Consider a single word. The Roman Canon prays for the dead in somno pacis — "in the sleep of peace." English can render the phrase, but the Latin carries an entire patristic theology of death-as-sleep, of the faithful as resting until the resurrection, that the English does not. When a Latin Catholic prays for his father in somno pacis, he is praying the doctrine of the Communion of Saints, the bodily resurrection, the intercessory power of the Church on earth for the Church suffering — all in three words. The translation gets you the surface. The Latin gets you the depth.

"But Vatican II said vernacular"

The most common objection. It is also the most common misreading of the Council.

What Sacrosanctum Concilium (1963) actually says is this: "The use of the Latin language is to be preserved in the Latin rites" (§36.1). And further: "Steps should be taken so that the faithful may also be able to say or to sing together in Latin those parts of the Ordinary of the Mass which pertain to them" (§54). The Council permitted vernacular for pastoral utility. It did not abolish Latin. It did not even prefer vernacular. It explicitly insisted that the faithful be taught to pray the Mass in Latin.

The implementation that followed often went much further than the Council intended — but the magisterial principle never changed. As recently as 2007, Pope Benedict XVI wrote in Sacramentum Caritatis that he wished "future priests, from their time in the seminary, [to] receive the preparation needed to understand and to celebrate Mass in Latin." Latin is not the Church's past. It is her ongoing liturgical patrimony.

What this means for you

You don't have to attend a Latin Mass to take lex orandi, lex credendi seriously. You don't have to learn to read Cicero. You don't have to memorize declension tables. But if the principle is true — and the Church has believed it for sixteen hundred years — then there are real consequences for ordinary Catholics:

  1. The Latin prayers belong to you. The Pater Noster, the Ave Maria, the Credo, the Gloria, the Magnificat — these are not optional traditional extras. They are the prayers in which the faith was deposited. Knowing them in Latin is knowing the faith in its native dress.
  2. What you teach your kids matters. If our children learn to pray only in English, with the inevitable shifts and revisions of translation, they will inherit a thinner faith than the one their grandparents inherited. The Church has always known this; it is why she has fought, in every century, for the integrity of her liturgical texts.
  3. The vocabulary is not a barrier. Twenty-five Latin words — gratia, Dominus, peccator, ora, mater, sancta, hora mortis, and a dozen more — are enough to begin praying the Roman patrimony with comprehension. Most Catholics already know half of them. The other half can be learned in a week.

Why we built Credo

This is the deepest reason Credo exists. We wanted Catholics — busy ones, lapsed ones, lifelong ones — to be able to walk back into the lex orandi of the Church without first having to enroll in a college Latin course. The prayers themselves are the teacher; you just need a small amount of help to start.

Start with the Pater Noster or the Ave Maria — both free in the app and on this site. Pray slowly. Listen to the audio. Let the words enter you. Within a week of doing this daily, you will begin to feel something the Church has known all along: that praying in Latin is not exotic, it is not antiquarian, it is not an aesthetic preference. It is coming home.