It is a religion book. Cyprian was the first who applied the term symbol to the baptismal confession, because, he said, it distinguished the Christians from non-Christians. Already at the beginning of the fourth century the Apostles' Creed was universally called symbol, and in the Middle Ages this name was applied also to the Nicene and the Athanasian Creeds. In the Introduction to the Book of Concord the Lutheran confessors designate the Augsburg Confession as the 'symbol of our faith, ' and in the Epitome of the Formula of Concord, as 'our symbol of this time. ' Symbols may be divided into the following classes: 1. Ecumenical symbols, which, at least in the past, have been accepted by all Christendom, and are still formally acknowledged by most of the evangelical Churches; 2. particular symbols, adopted by the various denominations of divided Christendom; 3. private symbols, such as have been formulated and published by individuals, for example, Luther's Confession of the Lord's Supper of 1528.