Disciplina arcani (Latin for "Discipline of the Secret" or "Discipline of the Arcane") is the custom that prevailed in the 4th and 5th centuries of Early Christianity, whereby knowledge of the more intimate doctrines of the Christian religion was carefully kept from non-Christians and even from those who were undergoing instruction in the faith so that they may progressively learn the teachings of the faith and not fall to heresy due to simplistic misunderstandings (hence, doctrines were kept from catechumens; Christian converts who had not yet been baptized).
In the second century, Christians freely communicated important rites such as baptism and the Eucharist with pagan groups. Justin Martyr, for example, freely spoke with a pagan audience regarding the rite of the Eucharist. The disciplina arcani began to emerge in the 3rd century. Some have suggested Tertullian as the earliest witness to the practice, although recent scholars have noted Tertullian's belief that Christian teachings were public and to be taught in public. Later, in the middle of the 3rd century, Origen of Alexandria addressed the polemics against Christianity by the pagan Celsus in his Contra Celsum. Celsus accused Christianity of being a religion of secrecy like the Greco-Roman mysteries, and Origen replied that while the prominent doctrines of Christianity are well-known to the entire world, including the virgin birth, crucifixion, resurrection, punishment of the wicked and rewarding of the just, there are a few elements that must be retained within the group. Near the time of Origen, Hippolytus of Rome wrote at the end of his account of the rite of baptism;
If anything needs to be explained, let the bishop speak in private to those who have received baptism. Those who are not Christians are not told unless they first receive baptism. This is the white stone in which John spoke of; "A new name is written on it which no one knows except him who receives the stone. (Ap. Trad. 23:14)
By the fourth century and first half of the fifth century, the practice of disciplina arcani had become universal and is attested in Rome (in the writings of Ambrose), Jerusalem (in the writings of Cyril and Egeria), Egypt, Constantinople, Cappadocia, North Africa, etc. There is evidence that Christians were careful to maintain specific articles of the religion, including removing members of the church who had not yet been baptized before the liturgical eucharist took place. Thus, the liturgy was divided into the Mass of the Faithful and Mass of the Catechumens. In Byzantine liturgy, the deacon would often make the proclamation "The doors, the doors!" in order to signal that the doors must be watched in order to prevent the unbaptized from participating in the activities of the church. There may have been various reasons that existed for maintaining the secrecy of some things, including ensuring that outsiders do not learn of them and attempt to use these rites to gain favours from God or shelter important rites from contempt. Furthermore, it was also thought that one needed to experience the rite of baptism before learning about it in order to make teaching more efficient and successful.
- Bremmer, Jan (2014). Initiation into the Mysteries of the Ancient World. Walter de Gruyter. ISBN 9783110376999.
- Yarnold, Edward (1994). The Awe-inspiring Rites of Initiation: The Origins of the RCIA. Liturgical Press. ISBN 9780814622810.