How are converts to the Orthodox Church to be received? What is the consistent patristic witness on the boundaries and identity of the Church vis-a-vis the various heterodox confessions? What have the Saints of recent times, especially from that ark of Orthodox experiential theology, Mt. Athos, taught concerning the one baptism unto remission of sins? This classic text, first printed in English in 1994 by St. Paul's Monastery on the Holy Mountain of Athos, explains how the canons from the Ecumenical and Local Councils pertaining to the reception of converts were understood by the Kollyvades Fathers and Fr. Constantine Oikonomos, among the most important theologians of 18th-19th century Greece. The Kollyvades Fathers, including the renowned St. Nikodemos the Hagiorite, emerged on Mt. Athos in the 18th century to guide the Faithful at a time of intense pressure and influence from the heterodox Latin West. Their witness and wisdom is of perennial importance, or rather of greater significance in our own day, as we continue to bear the weight of heterodox ideas regarding the Church. Fr. George Metallinos (1940-2019) was a leading theologian of the 20th century, former dean of the School of Theology of the University of Athens in Greece, and spiritual son of the Abbot of St. Paul's Monastery, Elder Parthenios. With the original English edition now out of print, Uncut Mountain Press has received a blessing from St. Paul's Monastery to publish this new edition with additional explanatory footnotes, so as to provide further clarification on difficult aspects of this topic, which remains of critical importance for the Orthodox Church today.