(Latin: "the law of what is prayed [is] the law of what is believed"), sometimes expanded as (Latin: "the law of what is prayed [is] what is believed [is] the law of what is lived"), is a motto in Christian tradition, which means that prayer and belief are integral to each other and that liturgy is not distinct from theology. It refers to the relationship between worship and belief. Its simplistic applicability as a self-standing principle independent of hope and charity was bluntly denied by Pope Pius XII, who positioned liturgy as providing theological evidence not authority.
The original maxim is found in 5th Century writer Prosper of Aquitaine's eighth book on the authority of the past bishops of the Apostolic See concerning the grace of God and free will: "ut legem credendi lex statuat supplicandi."
Credendi" and "supplicandi" are gerunds which are oblique cases of the infinitive, and so can be translated into English as "of praying/believing," or just "of prayer/belief," respectively.
Episcopal theologian Paul V. Marshall warns "many writers strip Prosper's original ut legem credendi lex statuat supplicandi of "ut" and ignore the function of statuat as the subjunctive of statuere, and so read the dictum as though it were an axiom.[...] (Prosper's) dictum evolved into the simplistic equation, lex orandi lex credendi, and liturgical material is employed in a hierarchical and sometimes authoritarian manner."[1]
In the interpretation of some, whereas the more general maxim "" suggests a general relationship between the two, Prosper of Aquitaine's formulation establishes the credence of certain Christian doctrines by placing their source in the Church's authentic liturgical rites, thus describing the liturgy itself as a deposit of extra-Biblical Christian revelation (part of a body of extra-Biblical beliefs known more collectively as Apostolic tradition), to which, in addition to Scripture, those who wished to know true doctrine could also refer.
As an ancient Christian principle it provided a measure for developing the ancient Christian creeds, the canon of scripture, and other doctrinal matters. It is based on the prayer texts of the Church, that is, the Church's liturgy. In the Early Church, there was liturgical tradition before there was a common creed, and before there was an officially sanctioned biblical canon. These liturgical traditions provided the theological (and doctrinal) framework for establishing the creeds and canon.
The principle is considered very important in Catholic theology. The Catechism of the Catholic Church states:
However, in the encyclical Mediator Dei, Pope Pius XII elucidates but strongly limits this principle and addresses errors that can arise from a misunderstanding of it. He states:
At a symposium held in connection with the publication of a set of reproductions of the first editions of the Tridentine liturgical texts, including the Roman Missal and the Roman Breviary,[2] Archbishop Piero Marini, former Master of Pontifical Liturgical Celebrations, presented a paper entitled "Returning to the Sources", in which he said:
Pope Bendedict XVI' Summorum pontificum (2007) quotes the Roman Missal that "the Church’s rule of prayer corresponds to her rule of faith " (emph. added.) rather than e.g. determining or causing.[3]
The inter-relationship of liturgy, belief and life has long been an issue for missionaries, such as the Chinese Rites Controversy, in particular relating to how liturgical and para-liturgical practices may need to be selected and localized to suit local sensibilities and meet needs.[4]
According to theologian Mary-Anne Plaatjies-van Huffel, whereas Catholic theology progresses from prayer to belief to life: lex orandi, lex credendi, lex vivendi, Protestant theology orders from belief to prayer to life: lex credendi, lex orandi, lex vivendi.[5]
The principle of lex orandi, lex credendi is found in Lutheranism.[6] Professor of theology J. Matthew Pinson writes that "Liturgical theology shapes the sermon, which in turn gives life to the Liturgy, preventing it from degenerating into dead ritualism, mysticism, or superstition."[7]
Anglican theology tends to be Augustinian and Reformed with a focus in the worship of the Church, and embodies a strongly evangelical liturgy.[8] Thomas Cranmer's reformed liturgy Book of Common Prayer[9] revised the liturgy following a principle of to propogate to English congregations the Reformed doctrines of grace and justification by faith alone.[10]
Eastern Orthodoxy's Patriarch Bartholomew I of Constantinople quoted this phrase in Latin on the occasion of the visit of Pope Benedict XVI, drawing from the phrase the lesson that, "in liturgy, we are reminded of the need to reach unity in faith as well as in prayer."[11] Rather than regarding Tradition as something beneath Scripture or parallel to Scripture, Orthodox Christians consider Scripture the culmination and supreme expression of the church's divinely communicated Tradition. Councils and creeds recognized as authoritative are interpreted only as defining and more fully explicating the orthodox faith handed to the apostles, without adding to it.