The rule of faith is a short summary of the gospel that, in the early Church, every catechumen learned by heart and recited before baptism. It stated the essentials: one God the creator, Christ incarnate, who died and rose again, the Spirit, salvation. Irenaeus of Lyon formulated it in the second century, and Tertullian gave it its Latin name, regula fidei.
An answer to heresy
The rule of faith was born in a time of crisis. In the second century, the Gnostics appealed to secret traditions reserved for an elite and offered their own readings of the texts. How could anyone know who was reading Scripture rightly? Irenaeus answered that the Church’s faith is public, received from the apostles and handed down in the Churches they founded. The rule of faith is its summary.
For Irenaeus, this rule contains the whole meaning of the gospel. Even someone who cannot read the Scriptures is saved by the faith it expresses. That mattered a great deal at a time when few people could read.
A safeguard for reading the Bible
Above all, the rule of faith serves as a reference point for interpretation. The Fathers liked to look for a deeper meaning in Scripture, sometimes through allegory. The risk was making the text say anything at all. So the principle was simple: any interpretation that contradicts the rule of faith is set aside.
According to the theologian Keith Mathison, this was the position of the early Church, which the Reformers wanted to recover: Scripture is the only source of revelation and the ultimate norm, but it must be interpreted in the Church and according to the rule of faith. Sola Scriptura therefore did not mean reading alone, without any reference point.
The rule of faith today
The course links the rule of faith to the kerygma, the basic proclamation of the gospel. The book of Acts gives several examples, such as Peter’s preaching on the day of Pentecost (Acts 2:14-41) or Paul’s in Pisidian Antioch (Acts 13:16-41). This heart of the faith belongs to dogma: it cannot change without serious consequences.
So the rule of faith is a reminder of something simple: reading the Bible does not happen in a vacuum. We read it in the light of the gospel we have received, with the Church of every age, and this protects us from readings that drift away from the heart of the message.