This Sunday, June 30, is the Feast of the Holy Apostles. They were the first appointed and sent out by Jesus Christ to bring his message of Good News and repentance to the world. They in turn ordained others to carry on this holy work, and as such, there is an unbroken chain of bishops throughout the centuries to the present. This is called Apostolic Succession. Apostolic Succession, in other words, is the tracing of a direct line of 1) apostolic ordination, and 2) Orthodox doctrine, and 3) full communion within the Church from the Apostles to the current episcopacy of the Orthodox Church.
The doctrine of Apostolic Succession originated early in the life of the Church, first articulated by St. Irenaeus of Lyons in the second century in response to certain Gnostics. The Gnostics were a group that claimed that Christ or the Apostles passed on some teachings secretly, or that there were some secret apostles, and that they (the Gnostics) alone were passing on these teachings. Their beliefs were an amalgamation of certain pagan religions and Christianity.
Irenaeus responded that the identity of the original Apostles was well known. The Tradition and lineage was not secret. The identity of the Apostles and their successors could be traced. Therefore, anyone teaching something contrary to what was known to be apostolic teaching was not a successor to the Apostles or to Christ.
In Orthodox theology, the unbroken chain of Apostolic Succession is significant because of Jesus Christ's promise that the gates of hell would not prevail against the Church (Matthew 16:18), and His promise that He Himself would be with the Apostles to the end of the age (Matthew 28:20). A disruption or end of Apostolic Succession would mean that these promises were not kept.
The Church remains true and right in doctrine and practice because of this promise, this God-given safeguard. Orthodox teachings today are the same as that of the first Apostles, though their mode of expression has adapted over the centuries to deal with emerging heresies, changes in culture and so forth. We should not be swept away by the whims of social change or culture or new age ideas. Rather, we should hold fast to the teachings and traditions handed down in each generation from the time of the Apostles till now.