St. Vincent was a monk of the Lerins monastery on the Ile Saint Honorat, in what is now France. He is known for several things. He wrote to proclaim the Orthodox teaching that Mary, Mother of Jesus, should be called Theotokos, or God-bearer, as she was officially called at the Council of Ephesus in 431. He also defended the Orthodox doctrine of grace and free will, which was being distorted in the Western church.
However he is most famous for his Commonitory which explained how we know to distinguish the Orthodox faith from doctrinal errors. He wrote that the Orthodox, catholic faith was what was believed “everywhere, always and by all.” In other words, in the Orthodox Church individuals do not ‘discover’ and teach their own individualistic teaching that they find when reading the bible on their own. On the other hand, in the Orthodox Church there is no infallible bishop or groups of bishops.
But we have to realize that this is not an exercise in archaeology. We don’t go back, let’s say to May 1st of 900 AD and take a survey of what every person in the church believed then. We do do this, but this is not the whole story. The Orthodox faith is not static. The fundamentals of Orthodox doctrine do not change over time. However, new questions and new challenges arise in the course of history and they have to be answered and resolved anew based on the unchangeable foundation of doctrines. What St. Vincent is telling us is rather that the Holy Spirit abides in the church and allows the church to always be faithful to the basics of the faith, while at the same time dealing with new issues. No individual, no matter how holy, comes up with doctrine on his own. On the other hand, no bishop or group of bishops can infallibly come up with new doctrines. It is always the living presence of the Holy Spirit in the church which keeps that faith whole and unimpaired. We can say that this was the meaning of St. Vincent’s Commonitory for us today.