Christian symbolism is the use of actions or objects to represent the truths of the Christian faith, either as a reminder of those truths or as a way of spirituallly connecting with the underlying truth or act.
The most important symbols in the Christian church are the sacraments. These rites, which vary between denominations but may include holy communion, baptism, ordination and marriage, are commonly described as an outward and visible sign of an inward and spiritual grace. In other words the rite is a symbol of the spiritual change or event that takes place within the participant. For example in communion the bread and wine are symbolic of the broken body and shed blood of Jesus, which in turn are representative of the death of Jesus which brings salvation to the recipient. The rite of baptism is symbolic of the cleansing of the sinner by God, and, especially where baptism is by immersion, of the spiritual death and recreation of the baptised person. The rite does not bring about the transformation, it is symbolic of the action of God.
Symbols were widely used by the early Christian church. Symbols were inscribed on Christian tombs from the earliest days. One of the most widely used in the early church was that of the fish, which derived from a Greek acrostic Jesus Christ, God's Son, Saviour. Interestingly the use of the cross (which is today one of the most widely recognised symbols in the world) as a symbol does not come until later.
In Eastern Orthodox churches icon paintings have symbolic significance.
Water has specific symbolic significance for Christians. Outside of baptism, water may represent cleansing or purity. Fire, especially in the form of a candle flame, represent both the Holy Spirit and light. The sources of these symbols derive from the Bible; for example from the tongues of fire that symbolised the Holy Spirit at Pentecost, and from Jesus' description of his followers as the light of the world.
Other Christian symbols include the dove (symbolic of the Holy Spirit), the sacrificial lamb (symbolic of Christ's sacrifice), the vine (symbolising the necessary connectedness of the Christian with Christ) and many others. These all derive from specific allegories in the Bible. Many are also used within Judaism.
Symbols drawn from outside
Also common in most Christian religious symbolism are emblems, figures or ideas drawn from the cultures which Christianity has superceded, so that symbols existing in those cultures have been adopted but embued with Christian meaning. The phoenix standing for the Resurrection, or the Egg representing rebirth, are examples of this incorporation of pagan symbols, for use in Christian art and customs. Often a pagan symbol was given a Christian meaning allowing incorporation of traditional practices into the faith of the new converts.
Diverse influences and meaning illustrated
The Christmas tree may be an interesting example of both streams of influence, converging together. Offering an explanation of these streams of meaning may illustrate how the interpretation of symbols is somewhat arbitrary and free.
On the one hand, trees that remain green in the winter have been symbolic of life in the midst of death, and of rebirth, in many cultures. The Christian folk-religious custom of erecting and adorning evergreen trees in the middle of winter was borrowed directly from existing practice, regardless of whether the custom had pagan roots. Some of the existing meaning has been carried over into Christian culture, together with these practices.
On the other hand, trees appear with symbolic meaning throughout the Bible: and the Christmas tree alludes to and builds upon this biblical symbolism. From the symbolic tree of knowledge of good and evil, concerning which the Fall of man and the curse of death came, to the tree of life from access to which mankind has been cut off, to the Oak of Mamre which "witnessed" the covenant made with Abraham and the renewal of that covenant with Joshua, to promises concerning the root of Jesse , the Branch, the Messiah, who was hung on a tree to bear the curse, and has been raised up again as a tree of life for the healing of the nations: the Christian story can be told from beginning to end in the symbolic terms of trees.
To focus on one stream of the development of this late Christian symbol, the Christmas tree symbolizes, in part, the promised "Branch", the Messiah, who must be the "Root of Jesse", the descendant prefigured by Jesse's royal son, David. The tree symbolizes the human geneaology of Jesus and especially his tie to David's royal line through Solomon, which had been perplexingly cut off by God from ever inheriting the throne, after Jeconiah. This connection to the cut-off line is symbolized by the cut-down tree, and is indirectly a symbol of the Son of God. According to Christian tradition, although a descendant of Nathan on his mother's side, Jesus is an heir of Solomon on his supposed father's side. In other words, if Joseph were in fact Jesus's father, then Jesus cannot be the Messiah, because Joseph is descended from Jeconiah, the cut-off line.
But through his mother, the genealogy of Jesus satisfies the promise of the Messiah in terms of human descent, and this is symbolized by the erect tree. It is an evergreen, because of his eternal origin as God, according to Christian belief. And yet, the tree is also customarily cut down before it is decorated, symbolizing that Jesus is also an heir of the line of Solomon by adoption, through Joseph. So, Christians think that God's word was miraculously fulfilled through the virgin birth, because in that way, the Branch came from the cut-off line of Jesse by adoption, and also by the living line of Jesse. By the birth of Jesus, the promise concerning Jesse's line has been fully fulfilled, Christians believe, and in this restoration Adam's line, all mankind, redeemed from futility and death, is symbolized. And that is why the Christmas tree is cut down, but restored erect, evergreen and clothed in light, in symbolic commemoration of the virgin birth.
However, this is only one of many explanations of this symbol, and not by any means the most common one. Not only the symbol itself, but also the meaning of the symbol is accounted for and explained in manifold and sometimes contradictory ways, according to various particular traditions. This flexibility and diversity in accounting for the history and meaning should be kept in mind, when considering any Christian symbol.