SYMBOL (Gr. o-uµ(3oXov, a sign)  , the term given to a visible object representing to the mind the semblance of something which is not shown but realized by association with it . This is conveyed by the ideas usually associated with the symbol; thus the palm branch is the symbol of victory and the anchor of hope . Much of early Christian symbolism owes its origin to pagan sources, the interpretations of the symbols having a different meaning; thus " the Good Shepherd with the lamb " is thought by some to have been derived from the figure of Hermes (Mercury) carrying the goat to sacrifice, and " Orpheus charming the wild beasts," which, when painted in the catacombs, was probably intended as the representation of a type of Christ . One of the earliest symbols of the Saviour, the fish, was derived from an acrostic of the Greek word jx06s, the component letters of which were the initials of the five words 'Irtaous X/narks, AEoO T16s, Eceenp, Jesus Christ, Son of God, Saviour . The ship, another early symbol, represented the Church in which the faithful are carried over the sea of life . Other symbols are those which were represented by animals, real or fabulous, and were derived from Scripture: thus the lamb typified Christ from St John's Gospel (i . 29 and 36), and the lion from the Book of Revelations, in which Christ is called the " Lion of the tribe of Judah." The peacock stood for immortality; the phoenix for the Resurrection; the dragon or the serpent for Satan; and the stag for the soul thirsting for baptism . The sacred monogram Chi Rho, , supposed to have been the celestial sign seen by the emperor Constantine on the eve of the defeat of Maxentius, represents the two first letters of the Greek word Xpu rros which Constantine figured on his labarum, or standard, and is found on early Christian coins, bearing also the favourite decoration of the Byzantine sarcophagi . The four evangelical symbols are taken from the book of Ezekiel and from the Book of Revelations; thus the winged man is St Matthew, the winged lion St Mark, the winged ox St Luke and the eagle St John; and these four symbols became the favourite subject for representation in the Church . Besides these the other evangelists and the saints carry emblems by which they may be recognized; thus St Andrew by the cross, St Peter by the keys, St Paul by the sword, St Edward by a cup and dagger, St Mary Magdalene by a box or vase, St Lawrence by a gridiron, St Faith also by a gridiron, &c .