Lex orandi, lex credendi

Lex orandi, lex credendi (Latin loosely translated as "the law of praying [is] the law of believing") is a motto in Christian tradition, which means that it is prayer which leads to belief, or that it is liturgy which leads to theology. It refers to the relationship between worship and belief, and is an ancient Christian principle which provided a measure for developing the ancient Christian creeds, the canon of scripture and other doctrinal matters 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 framework for establishing the creeds and canon.

An early account of the maxim is found in 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, "Let us consider the sacraments of priestly prayers, which having been handed down by the apostles are celebrated uniformly throughout the whole world and in every Catholic Church so that the law of praying might establish the law of believing".

The principle is considered very important in Catholic theology. The Catechism of the Catholic Church states: "The Church's faith precedes the faith of the believer who is invited to adhere to it. When the Church celebrates the sacraments, she confesses the faith received from the apostles – whence the ancient saying: lex orandi, lex credendi (or: legem credendi lex statuat supplicandi, according to Prosper of Aquitaine). The law of prayer is the law of faith: the Church believes as she prays. Liturgy is a constitutive element of the holy and living Tradition."

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, Archbishop Piero Marini, former Master of Pontifical Liturgical Celebrations, presented a paper entitled "Returning to the Sources", in which he said: "It is above all in the Liturgy that renewal cannot do without a sincere and profound return to the sources: sources of that which is celebrated and sources of that which is believed (lex orandi, lex credendi). Digging deep into the sources, the theologian and the liturgist aim simply to penetrate the profundity of the mystery of the faith as it has shown itself in the concrete life of the Church all through her history."

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