What Theologians Have Argued for Lex Orandi, Lex Credendi?
The Patristic Period. As noted above, Prosper of Aquitaine is the first to have elucidated the lex orandi-lex credendi principle as a maxim. Wainwright notes that other Patristic writers used the idea extensively as well – he specifically mentions Augustine, Ambrose, Irenaeus, Tertullian and Cyprian. One author he oddly mentions only in passing is Cyril of Jerusalem, whose Mystagogical Catecheses were delivered as sermons to those newly baptized at the Easter Vigil during in Easter Week. It was the practice of the early Church to dismiss the catechumens from the Eucharistic assembly after the sermon and prior to the Intercessions, and so they did not know much, deliberately so, about what to expect at their Baptism. Each of Cyril’s sermons was on a different part of the Baptism, Chrismation, and First Communion rites the newly baptized had just experienced at the Vigil. Cyril himself wrote,
I have long been wishing, O true-born and dearly beloved children of the Church, to discourse to you concerning these spiritual and heavenly Mysteries; but since I well knew that seeing is far more persuasive than hearing, I waited for the present season; that finding you more open to the influence of my words from your present experience, I might lead you by the hand into the brighter and more fragrant meadow of the Paradise before us…
Prosper of Aquitaine is the first to have elucidated the lex orandi-lex credendi principle as a maxim
In each of the five lectures, entitled “On the Mysteries,” “Of Baptism,” “On Chrism,” “On the Body and Blood of Christ,” and “On the Sacred Liturgy and Communion,” Cyril chose to allow the candidates to experience the liturgy first, and then he explained the theology of the liturgies themselves, an approach that clearly exemplifies a lex orandi-lex-credendi liturgical theology.
The Scholastic Period. Liturgy and theology continued to develop over the centuries, and by the time of the Scholastic period and the revival of Aristotelian philosophy, there was a great desire to systematize the body of Christian theology. Thomas Aquinas was perhaps the pre-eminent theologian who did so in the area of liturgy. He helped define the “form” and “matter” of sacraments and began their enumeration. As the Mass became less accessible to the people, as it was in Latin and most didn’t understand it, it became less of a source of formal theology, while Aquinas and others began to separately compile formal systematic theologies, which included sacramental theology, often rather distanced from the rites themselves. As Msgr. Kevin Irwin notes, “for Thomas, liturgy was regarded as one of the auctoritates for theology, alongside Scripture and Aristotelian philosophy…. Liturgy continued to influence theology, but more as rites performed for the people, than by and with the community.”
The English Reformation. Archbishop Thomas Cranmer was aligned with the Continental reformers Luther, Calvin, and Zwingli in his desire to simplify and correct the liturgies of his time. The Sarum Usage in particular, the most widely-observed liturgical use in England at the time, was a “rather exuberant, elaborate, beautiful, and especially well arranged adaptation of the Western or Roman Rite.” But it was complicated, and Cranmer wanted to get the people more directly involved. In Cranmer’s own words in the Preface of the First (1549) Book of Common Prayer, “…many times, there was more busines to fynd out what should be read, then to read it when it was faunde out.”
All the Reformers essentially switched the order of lex orandi and lex credendi and worked on their doctrine first.All the Reformers essentially switched the order of lex orandi and lex credendi and worked on their doctrine first, and then modified their liturgies to reflect that doctrine. Cranmer was no exception, although he did not write a treatise or compile anything akin to the Augsburg Confession or even the later Westminster Confession. He simply went right to the worship books themselves, radically conflating the seven Daily Offices into two, making moderate changes to the Eucharist, and putting it all into the English of his day, in one single bound book, with the power of the State behind it in the Act of Uniformity. The 1552 and 1559 Books would be more Protestant, but by the time of the Restoration and the promulgation of the 1662 book, then as now the standard English Book, there was a consensus about how much reform would be accomplished and what was too much. If the Patristic period was the zenith of lex orandi, then the Reformation was the same for lex credendi.
About the same time, there was a similar ascendancy of lex credendi in the Roman Catholic Church as defined by the Council of Trent (1545-1563), where for the first time a clear separation of liturgy from sacramental theology was evident: “Liturgy became equated with the external performance of the Church’s rites. Sacramental theology was incorporated into manuals of dogmatic theology that paid little attention to the rites themselves as a theological source.” The claims and counter-claims of the Reformation reduced the liturgy on both sides to the tool of the theologians, regardless, especially on the part of the Reformers, for much pastoral sense of what was being lost.
 Cyril of Jerusalem, “First Lecture on the Mysteries”, trans. R. W. Church and Edwin Hamilton Gifford in A Select Library of the Nicene and Post-Nicene Fathers of the Christian Church, Second Series, Volume VII: S. Cyril of Jerusalem, S. Gregory Nazianzen, ed. Philip Schaff and Henry Wace (New York: Christian Literature Company, 1894), 144.
 Kevin Irwin, “Lex Orandi, Lex Credendi – Origins and Meaning: State of the Question,” Liturgical Ministry, Spring 2002, 63-64, emphases in original.
 Robert J. Wright, “The Sarum Use,” The Anglican Society website, https://sites.google.com/a/anglicansociety.org/the-anglican-society/president-s-corner, accessed 11-28-12.
 Wainwright 263-270
 Irwin 64