Kallistos Ware, We Must Pray for All: The Salvation of the World According to St Silouan

"If those in hell are not deprived of God’s love, if they are embraced also by the love of the saints, may it not still be possible for them to respond to this love that surrounds them on every side? Is there not still a hope that they may ultimately be saved? St Isaac certainly seems to have believed in universal salvation:[7] as a member of the Church of the East, dwelling safely beyond the confines of the Byzantine Empire, he had no reason to fear the anti-Origenist anathemas of the Fifth Ecumenical Council (553)."